Hobo said:
Otherwise, though, you're saying that all games with the exception of some really bleeding edge indie games are fundamentally exactly the same.
Well, I don't know if I would say "all," but I'm not going to deny a) that there are a lot of RPGs that look similar to me, and 2) the indies happen to be the main ones that are actually pushing the envelope right now, so, yes, I see greater differences there.
But, for the sake of argument, let me pick two totally mainstream RPGs and compare them: D&D (specifically, not d20 in general) and HERO.
In D&D, PCs advance by killing things; it's the primary—and most rewarding numerically—way to earn XP. D&D PCs also tend to be heroic and more powerful than Joe Commoner.
In HERO, PCs advance simply by participating; they earn EPs simply by being present in a scenario, and can earn more for "good roleplaying." The power-level of HERO PCs is very dependent on the campaign guidelines; they could be invincible, they could be easily killed.
I'd argue that a horror game, like CoC, will play out differently with each of these two systems. D&D players will have a huge incentive to "win," and will likely have the means to do so. HERO players may or may not have the ability to survive, and they will be rewarded whether they "win" or not.
Also, I've played a good amount of fantasy with HERO, and it doesn't feel like D&D to me at all. However, it did feel a lot like some old Rolemaster games I've played, which is more in the "sim" camp with HERO.
So, there you go.
The other factor in play is how the RPG in question is being used. You said in your original post that you're not big into rules. I'm going to assume that means you're happy to leave the rulebook behind and go with the flow. I.e., your "system" is your rapport with your group of players, and that trumps what's written on paper.
If that's true, then, yeah, different games are going to look very similar, precisely because your own free-form story/setting system gets ported to every RPG you use.
The HERO group I was in basically operated in this manner. The few times we played other RPGs felt almost no different, because, honestly, we were ignoring the rulebook no matter game we were nominally playing.
The D&D groups I play in, and most of the Gameday events I've played/run, are very different from this. In those contexts,
Iron Heroes, e.g., feels quite different from D&D, which feels quite different from True20... and all of which feel absolutely nothing like
Burning Wheel.