Sorted by generation...
NES #1 - Obtained in 2003(?). Model number and manufacturing date seems to indicate that it's an early Canadian model, making it in commission since 1986. Still works, but in order to remove cartridges, pliers are required (the cartridge slot is modified so the contacts are so tight that simply pulling on the cartridge will not remove it).
NES #2 - Obtained in 2004. I have no idea how long it's been around; looks like a really old USA model. No longer works; produces a blinking light or a white screen.
Overall, I would say that the NES is about a 6/10 on the reliability scale considering the age.
Sega Master System - Obtained in 2001. Very old; It's an SMS I. Both the card and cartridge slots still work. The controllers seem to predate electricity and still function correctly.
The SMS is a 10/10 on the reliability scale because I've heard of them breaking but not nearly to the extent of the NES. Considering how many of these beaten motherfuckers exist in South America while maintaining functionality after somewhere around 25 years it's hard not to call it one of the most reliable consoles of all time.
Sega Genesis #1 - Obtained in 1991. Second generation Genesis I (no "high definition graphics" printed around the cartridge slot, no serial port on the back). This Genesis has seen untold amounts of terror: A controller was ripped especially hard from one of the slots rendering the female side of the plug useless (we later fixed this and now it works fine) and over the years the quality of the RF connection has gone down noticeably. Still plays games perfectly to this day.
Sega Genesis #2 - Obtained in 1996. A launch Genesis I from when the Genesis was only sold in major cities in the states (High definition graphics printed on the console, serial port on the back), this has most certainly been around since the launch of the Genesis. I've played this particular console more than any other console ever and it still works perfectly. Virtually no damage to the video quality although the cartridge slot is becoming less reliable by the year. Oddly fragile to being disturbed while the game is in progress though (moving it is not recommended).
While the Genesis never breaks, it sure is susceptible to a lot of weird problems. Otherwise I would say 9/10, easily one of the most reliable consoles ever built.
Super Nintendo #1 - Obtained in 1998. I have no idea how it got there, but this was found in our attic. Seems very early. I've since had to shield this console due to the risk of UV discolouration. It's still pretty damn purple, though. Plays games perfectly although the cartridge slot is getting unreliable.
Super Nintendo #1 [Famicom] - Obtained in 2007. I know nothing about this, other than that it works perfectly and that when I bought it the UV damage was already extensive and the console is pretty yellow.
Other than a cheap outer shell and an unreliable cartridge slot, the console seems more solidly constructed than most. 8/10.
Nintendo Game Boy #1 - Obtained in 1996. A grey, very early model. This thing has been scratched to the point where the screen is almost completely covered in surface scratches. The cartridge slot still works but is finicky. Other than that, it works great despite all better logic.
Nintendo Game Boy #2 - Obtained in 2003. Red, slightly newer than the aforementioned. Used to belong to my sister; certainly in much better condition than mine. Works perfectly, although again, the cartridge slot is a little finicky.
10/10. No portable system should last this long. Period.
Nintendo Game Boy Pocket - Obtained in 2008. Transparent, barely used. Works perfectly.
9/10. A little bit more breakable by design than the fat model; I also know of at least one that has lost the functionality to be used with batteries.
Sega Game Gear - Obtained in 2000. Bought used, I have subsequently extensively used it; it's a first generation model as indicated by the markings on the screen. Screen works perfectly but that's about it. The speaker no longer... speaks (although headphones work fine) and the cartridge slot is very unreliable although still functional.
Still fairly strong for a portable that was far too powerful for when it was released but the amount of things on it that have broken is still pretty large. 7/10.
Sega Saturn #1 - Obtained in 2003. When I bought it, the memory backup was dead.
Sega Saturn #2 - ...And then I went back a week later, exchanged it for another one. Memory backup also dead.
Sega Saturn #3 - It's at this point that I caught wise and realized that the console contains a swappable CMOS battery conveniently locatable through a small compartment in the back. Works perfectly to this day although for some reason it shorted my backup RAM cartridge.
The bizarre decision on Sega's part to make the internal memory entirely reliant on a CMOS battery makes it hard to call this console reliable, despite the fact that they seem to never break (if the amount of them floating around is any indication). Also, the shorting my memory cartridge thing was a little weird. 7/10.
Nintendo 64 - Obtained in 2004. A fairly late model, still works great. It's never given me any trouble.
Too soon to tell. I don't use it enough.
Game Boy Colour #1 - Obtained in 1998. Part of the first wave of new colours; teal. Haven't seen it in at least eight years.
Game Boy Colour #2 - Obtained in 2007. Pink, don't know enough about the chronology of GBCs to say for sure where that puts it in the timeline. Other than the fact that the battery cover no longer really sticks, it works perfectly.
I honestly don't have enough experience with the console to judge.
Sega Dreamcast - Obtained 9/9/99 (baby). Launch model. Still works perfectly despite all better logic; it's seen more CD-Rs than the Dreamcast was ever intended to. It seems rather loud when reading discs, but then again, all Dreamcasts doo.
9/10; this is a really difficult console to break unless you use a lot of CD-Rs.
Game Boy Advance - Obtained 2001. Launch model (white). Used extensively, the screen is scratched to all hell but otherwise the console works great. Only exception is that the flimsy triggers don't trigger like they used to.
8/10. They really need to work on those damn triggers.
Sony Playstation 2 - Obtained 2006(?). I've only used it lightly but it seems to work fine... for now.
3/10. Launch failures, DRE. Two things that shouldn't happen.
Game Boy Advance SP - Obtained 2003. Launch model. The clamshell was very compatible with me and this became the first GBA I owned to not be scratched to hell. The battery life is less than half of what it was when I bought it; otherwise it works great.
9/10. Li-Ions are dumb.
Nintendo Gamecube - Obtained 2005. The controllers don't seem built for extensive use (the analog sticks loosen up too easily and at least one of my C-sticks doesn't recognize properly). Otherwise, works great.
7/10. It's rare for a console to outlast its controllers; I have a Genesis controller with the C button missing that still works (we use it to play Ms. Pac-Man).
Nintendo DS - Obtained 2004. Launch unit. The story behind this one is a little bizarre: I got it at launch and then had it stolen from me shortly before the launch of the DS Lite. It was stolen by a guy I knew who subsequently gave it back a few months later but in worse condition. Despite nearly breaking the hinges and scratching up the bottom screen, this still works great.
10/10. If a drug addict can steal it, attempt to break it (or at least make it look like he attempted to break it), and then return it, it's a durable console.
Nintendo DS Lite - Obtained 2006. Launch unit. Still working fine.
This hasn't been through enough to get a rating.
Sony PSP - Obtained 2005. Launch unit or early release; PSP-1000 that does not have one of the originally mod-unfriendly motherboards. Suffered extensive softmodding and still works. Reads UMDs despite being stuffed in my bag with the drive open by mistake once. Only flaw seems to be that the analog stick stick fell off so now it's just a nub.
8/10. The stick falls off too easily; otherwise, the fact that this console seems immune to software breakage is worth something (despite the fact that this is largely because of its community).
Nintendo Wii - Obtained 2006. Launch unit. Works great if you ignore the fact that mine makes an unusually large amount of noise (it sounds like it's trying to read sandpaper) and that the sensor bar is missing a light.
7/10. I've never been more afraid that one of my fully functional consoles is breaking.
Sony Playstation 3 #1 - Obtained 2008. 80GB Non-BC. Ylod after nine months of usage. Sony charged me $150 to fix it because they wouldn't accept my Future Shop receipt as PoP on account of the fact that over nine months the already faded receipt faded further, so I took it to a guy who fixed it for $85 instead. Read on.
Sony Playstation 3 #2 - Obtained 2009. 80GB Non-BC on a 160GB Non-BC motherboard. After less than two weeks, it started to shut itself off sporadically. I was told that my repair didn't cover unrelated damages. I opened it up to discover that the connector for the power supply cable was barely connected to the motherboard. This PS3 no longer works.
Sony Playstation 3 #3 - Obtained 2009. 120GB Slim. Works great.
2/10. I realize that I am partially at fault for taking my PS3 to a guy as opposed to Sony, but no console should be so prone to breakage that a good percentage of them aren't lasting within their warranty period let alone their period as a current-gen console.