Off the top of my head: more talented players at nearly every position; more advanced systems, schemes, and play calling; playoffs.
College ball does have the advantage of more intense rivalries (OSU-Michigan), but that’s due to the NFL’s team realignment in 2002. Even with that, it’s hard to beat some NFL rivalries: Dolphins-Jets, Patriots-Colts, Eagles-Giants, and Bills-Winning to name some. (Cowboys-49ers used to be damn good.)
I think there is a certain sort of romanticism with the college game that appeals to fans. E.g.: I love minor league baseball...well, because I’m a nerd, but even though pitchers and hitters in Single A don’t have the talent that players in AA or Triple A, let alone the Major League level have, there’s always that “hey, I saw that guy when he was in Single A Boise and couldn’t hit a fastball with a 2 x 4” story I can tell people in passing.
(That and it’s a really fun way to take three hours of your day and just get absoutely drunk. :) ).
Oh, that reminds me, I got a question for you. I’ll FReepmail you.