For me, easily at the stadium. Being from out of town, I get to go to about one game a year, so it's a real treat to watch the game inside that beautiful stadium. And there's nothing like watching the Irish beat down an opponent with 80,000 of your closest friends.
Now, for other sports, I agree, I'd rather watch them from home unless I have GREAT seats. This way I avoid the traffic, paying for parking and food and beer, and not being able to see the game and/or replays with a great view. At home or at a buddy's house I get the BBQ, the big screen, the beer, the bathroom, etc, all within a few feet.
But for college football...the tailgating, the craziness of the students and fans, the anticipation, just the whole atmosphere...there's simply nothing better.