First, I want to reiterate that neither Tekken or UFC are "grapplers." They're fighting games without projectiles (well, mostly, in Tekken's case) and they're pretty similar on the surface, until you get into UFC's ground game, which is actually a fairly unique mechanic within the genre.
I LOVE Tekken... but Tekken is NOT a "balanced" fighter at all. (Pick any character with the last name "Mishima" or "Kazama" and you're pretty much set...) And yet, it has a very steep learning curve (not as ploddingly slow and onerous as Virtua Fighter's, but not too far from it) before you get to the point that a button-masher actually stands no chance against you. Paradoxical, I know, but that's how it is!
It sounds to me that UFC is right up your alley. It's a good game, with familiar characters, an unpredictable fun element (Flash KOs/tap-outs, etc.) I haven't played 2010, but I played the hell out of 2009, and I think it fits your criteria of possessing balance for players of equal skill while also providing enough depth that a noob cannot just button-mash and win (they *might* win with a well-timed HEAD KICK, though, just like real life!) In general though, in the UFC games, if somebody is button mashing, you shoot on them, get the takedown, wear them down, and make them tap like the bitches they are!

I think all fighting games have those certain things people will want to spam (that damn HEAD KICK!) but there are finesse counters available to someone who takes the time to learn the engine. UFC most reminds me of Bushido Blade for the PS1... if you've ever played it, you probably understand what I mean. No matter what your skill level,
you might lose, but it never feels "cheap."
By the way, I know UFC 2009 didn't allow weight class mixing (2010 might,) but I know for a fact the Fight Night series does (Ali vs. Pacquiao, either way, is FUN FTW!) That said, in much the same way UFC has uprooted boxing's dominance, the UFC games just have more Fun value than the traditional boxing games (unless you're REALLY invested in boxing.) I'd leave Fight Night on the shelf if I were you...
The good news is that all of the games mentioned at this point can be found for less than full retail prices (the only "new" fighter right now is SSF4AE) so I don't think it'll hurt you too much to try more than one!