I wouldn't say it's an "us vs. them" situation at all.
Nintendo makes the best titles for their system for the most part. When third parties actually take the effort to make something worthwhile/decent for the GC, then they're generally pretty well rewarded. Especially where exclusives are concerned. I'd say that games like RLII, Monkey Ball, Resident Evil, Sonic, and even more recently titles like Godzilla have done pretty well on the little box.
Granted, some titles suffer for a reason. You cited Timesplitters 2 for example. Well, that's great and all, but think about this: The title released two weeks after the other versions. Do you remember the commercial for it? At the beginning there's a huge splash of "First Halo, now this!"-Official Xbox Magazine and then at the end of the commercial, it had a HUGE PS2 logo, a medium size Xbox logo, and a tiny GC logo. Also, I remember trying to buy it for GC- I had to SPECIAL ORDER it because stores were on "shipped a pathetically small amount and there was no idea when they'd be able to get more" for the game. Straight from a Gamestop manager's mouth.
So, when a company doesn't promote that it's even on GC, ships a pathetically small amount, and ships it later than the other versions they have no reason to grumble about it when the title sells poorly. Granted, this situation has been getting better, but I've had this problem buying several GC titles, including but not limited to: Mortal Kombat, Timesplitters 2, Two Towers, Tony Hawk 4, and a couple others I can't remember offhand.
Do I blame Nintendo? Hardly.