While I can't say the same about most of the people who vote in these polls, I own both of these games. However, I haven't gotten to playing MGS3 yet. I bought the pack that had 1, 2, and 3 in it, and I'm still working on 2 (along with the long list of games I'm playing right now). While I do think it's a fun series, the fact that you're rewarded most for killing as little as possible doesn't appeal to me as much as it would if you could pick some guys off while you were sneaking around. I still thoroughly enjoy the series, but not enough to vote it over THPS.
While this is nowhere NEAR the best entry in the series, I still really, really enjoy busting out the original every now and then. Reverts, and more importantly, manuals weren't implemented into the series yet, so linking 100x multipliers were near impossible for a single trick, but I still managed to break 1,000,000 on the warehouse in under the two minute time limit. While this game might seem pretty boring for a casual, when you've really mastered the controls of the game and you're playing against a few people who've done the same, it's still one of the best gaming experiences I can have. I mean sure, I'll usually just bust out THUG2 and do the classic mode on there (Canada <3 man THPS3 was the shit), but that doesn't mean I should discredit this particular game like a certain debater has been doing throughout the tournament.
Vote whatever title you prefer most, I really don't give a shit over this one, they're both great games.