The thrill of the hunt? Not so much anymore. Going to non-Game Stop stores isn't nearly as fun as it used to be since nearly all of them enjoy hiking up their prices or matching them on eBay. It used to be fun, though.
The feeling you get when you find a good deal on something? This is fun when it's at a convention.
Enjoyment from playing the games? This is the biggest one. I'm a gamer first. Collecting is just an after effect of my gaming habit.
The community behind it? There will always be a few jerks that can sour things for everyone, but the community at large is great. This website, for example, has its share of wonderful people.
The nostalgia? Nostalgia helps. It's fun finding a game you used to play. It's just a shame when said game is really expensive.
Just having something to do, the hobby of it? It's a fun hobby. But, not as fun as gaming.
Just something to spend money on? Nah. Just throwing money at something just because is not something I do.
Bragging rights? Absolutely not. If someone is impressed by something I have, then that's cool. But, I didn't buy it just so I could be like, "Look what I have and you don't."