I totally disagree with this. Binding of Isaac is not only beatable without using any unlocked items or characters, it is probably still easier than Spelunky. The initial character and items make the game both fun and winnable (except that I believe the game won't let you face the further levels right away, even though you could have beat them). It's nothing like Rogue Legacy, which on the contrary is both unfun and essentially unwinnable without grinding.
The real difference with items is their function in the game. Getting weird combinations in BoI and trying to make them work is fun. There is no "optimal" item set that you would want to get every time. My favorite run I didn't even win, but the item combination was great. Unlocks are probably there mainly to encourage the use of more combinations, not to make you stronger.
In Spelunky most people will have an optimal set they want every time. I don't ever think "hmm, I hope I don't get a jetpack this time." I always, always want a jetpack. A jetpack alone is sufficient to beat Olmec without much danger even if you had 0 other items/ropes/bombs and 1 health. (though unless you are a super expert you would need some bombs in the temple, less if you had the shotgun).
I think this results in BoI being less frustrating (since new combinations are fun even if you lose). But Spelunky's randomized level design is on a totally different level. It's absolutely amazing how many possible situations there are for you to (quickly) analyze and try to defeat, and given that how rare it is for anything to feel unfair (fire frogs swarming the inside of shops in a dark level black market, kinda felt unfair). And I haven't even made it to the real last level yet, just started trying that yesterday.
Well, I should've been more clear.
First off, I feel Rogue Legacy is the wrong way of handling unlocks in a "rogue-like" game like the ones we're discussing. While I did draw that parallel with regards to The Binding of Isaac, it ultimately revolves around a vaguely similar idea to grinding BUT with more fun, thought and combinations involved thanks to (as you pointed) the variety of builds you could try to mix-and-match. Can you still reach Mom on a completely fresh save with nothing major unlocked, so long as you have the experience already? Sure, but there's still a good chance that the game isn't very generous with your first drops which (for an experienced player) usually results into resetting if he doesn't get anything decent during the Basement and the Caves stages. The actual game itself isn't difficult once you know the ropes and even for newbies it's easy to get the jist of it conceptually, but a good number of strong items
need to be unlocked through different requirements; achievements, challenges, x completed runs, ...
Perhaps this is just an unfortunate personal anecdote, but that's how it went for me. I started playing Isaac already knowing a large chunk of what to expect and what to do, and after 2 hours the gameplay's intricacies were already natural to me on top of me not really being threatened all that much by the enemies / bosses the game throws at you initially (as the harder stuff only gets unlocked later too). Sad part being though, I still had a lot of difficulty reaching and finishing off Mom, primarily due to underpowered builds and my tiny item pool for the RNG to choose from. Lack of in-game knowledge and not having honed my skills enough yet weren't the issue in my position, as explained earlier. The rate of my progress only spiked after a dozen hours, and the rate at which I was 'improving' was directly tied to having had runs where my damage output was no longer lackluster so that killing Mom became more practical and time-efficient. Which in turn lead to another batch of good unlocks as I stubbornly marched onwards for the next finish line. Only then did Isaac 'click' with me.
Given the restrictions Ed McMillen had to work with due to Isaac being based on Flash, the sheer number of items available to you to unlock (as well as enemy tiers) was a smart method to compensate for the kind of stages or general obstacles being more static than he would've liked, so perhaps it was unfair to put Isaac next to Rogue Legacy. However, the above is not without its glaring downsides, as the
real fun and the
real 'sandbox' nature of Isaac (in terms of items, enemy spawns, etc.) only opens up after investing not-so-insignificant time into it, rather than the purest sense of skill being the main barrier to entry (like Spelunky). Not to say Spelunky doesn't have its problems (some extremely situational items for example), but in games where you will end up dying repeatedly I prefer everything already being open to the player
in theory, provided one has the necessary chops to back it up. Dark Souls also fits the bill here, but that's a different topic altogether.
tl;dr --- I had fun with The Binding of Isaac (unlike Rogue Legacy) with 63+ hours clocked in and I'd still recommend it to new players, but being artificially locked out of the 'true' experience isn't
my cup of tea. Spelunky and it are at opposite ends of the "rogue-like" concept and that's okay, different things appeal to different people, but whenever Rebirth comes out I'm not looking forward to my first dozen hours unless Ed McMillen tinkered around with making player progression a tad more consistent and... gradual. Only when starting out, that is.
I just beat Yama for the first time! I used the last of my bombs on Olmec and had zero the rest of the way until the throne. With a record of 1-437, I'm about ready to turn pro.
Sweet! Going through Hell without any bombs must've been brutal.
I'm still in it, 114+ hours on steam, though I'm running out of stuff to do. I think the last thing to do is play for the leaderboard and do an eggplant run. I don't think I've cracked a million yet, either, I think I should try that.
Congrats! I think that's easily the hardest achievement to get. I just got it a few days ago myself.
I'm in the same position now. Gonna try and accomplish a solo eggplant run, though given the strict initial requirements I should also be trying to simultaneously one-up my 1,2 million highscore (rather than endlessly resetting) if things don't pan out in the mines.
Which I could throw at normal spiders and it kills them.