stadium anyway. The sights, sounds, smells is part of the experience outside of the obvious experience of cheering on your team in person and creating a nice home advantage for them. The opponent is actually only part of the equation for me. I've been to some pro baseball games and the game's were nice, but the atmosphere was fantastic.
If I had the money and time to be a season ticket holder I'd want the tickets for many reasons, and the opponent is only one among many of those reasons, so I'd still buy them for the experience... especially when it would offer an opportunity to go out and do something with my kids.