I think the humor and vibe of Bully alone is worth the price of admission. While many of the missions are pretty fun, it's also one of those games that lets you have fun your own way. The controls and camera work are a little dated by today's standards, but the various school themed weapons are a breath of fresh air compared to your usual guns, and while the melee combat isn't exactly Platinum Games tier, it gets pretty engaging as you unlock new moves.Vice City gets a lot of love from me because it's the only GTA to make you feel like an actual criminal. The controls are outdated and the game has aged badly, but there's something enjoyable in having a GTA protagonist actually take some initiative and build his own empire instead of doing other people's dirty work. It's also got unquestionably the best soundtrack in the series and the city itself is so much fun to travel around in. It's the only GTA I've ever finished, and the only one I ever felt compelled to start trouble in.
San Andreas is too goddamn big for its own good though. Especially when you get out of the Grove and have to travel across the map to do different missions. That and the plot flies off the rails right around the time Mike Toreno shows up. I gave up entirely when I had to do the shitty plane missions.
I've always wanted to try Bully though. A lot of users on here seem to love the hell out of that game.
Even though the game isn't as modding friendly as some of the later GTA titles, there's still a dedicated modding base that has come up with some really fun stuff (like Insanity edition, the Fight Club mod or custom missions Bullies' Nightmare and The Cure), for which I'm usually in favor of Scholarship Edition on PC\Steam. In case you decide playing the PC port it also doesn't hurt to install a fan-made patch known as silentpatch:
While it was mostly made for Windows 10 users, it also remedies other problems common on earlier versions such as glitches or the game randomly shutting down. Even if you're playing on Win7 ir 8, it's a good idea to have this patch ready in case things aren't working out the way they should.