NES - SMB, everyone had this game! It was as common to me as morning cereal. A little tyke, just laying in front of the tv in my tighty whites going through Mario. Played it on christmas videos we have, when there was nothing to do.. It was entertainment and the best thing on the system to me. Whole reason I had one.
Genesis - Sonic, the first real against the norm system. For the cool kids. Sega tv, Sonic.. I remember you could ask a class which system they had and it would split right down the middle between Genesis and SNES almost every time. Oh, and when my best friend's Snes busted and he got a Genesis. I was so pissed at him, the trader
SNES - Super Mario World/name Nintendo. I just knew games were nintendo, nintendo was games. SMW was also great, I loved everything about that game. My cousin and me would just go nuts with this game. Played it a half hour before school for so many mornings. Fond memories
PSX - Number one, it was a new system which was an amazing leap. And if I could find the right game I'd be on board. For me it was Tekken 2, seeing an arcade in my house. Big screen no less. But historically, this was FFVII's success
N64 - Super Mario 64. That started it. I had to have one once I'd seen it in motion. Absolutely beautiful. But it eventually came to a point where Goldeneye was a huge system seller. I remember once it got popular, that game spread like wildfire. Any group of friends played that to death. Just goes to show people love a game that has guns and brings the multiplayer in you out.
DC - Again, being the first next gen. But other than that, it was NFL2K, Sonic, and Soul Calibur's amazing graphics. Just one sexy machine, and great advertisements imo. A damn shame it didn't last. This system rocked. Such a sleak design that spoke next gen at the time.
PS2 - MGS2. PSX brought a ton of games to my attention. MGS was maybe the best. Just a spectacular game, and when you seen mGS2's visuals and hype you couldn't stay away. I'm not sure I got as hyped for a game as this. Also, GTA was such a cool game back in the psx games. I got quite a few hooked on it but it never spread. So I couldn't believe the PREVIEWS. I still have it's premiere preview in GI and I remember thinking how much this game would rock. And it did, I had it right away, and BOOM. Everyone loved it. Definetly a system seller.
Xbox - Halo. The word of mouth on this board alone was crazy. I remember not being that impressed with it after I bought it. Such a pocket full of money to throw down. However it paid off after some time, and Shenmue II eventually came which was partly a system seller for me.
Gamecube - That was the problem.. they had not a single franchise game to launch with or talk about in near future. Closest thing was Super Smash Bros Melee but for me I was sold on Nintendo still. In the end, Resident Evil became the best reason to own this system, though hopefully the next Zelda changes that.