/shrug, I haven't played tf2 (although I do own the bundle it came with, just never bothered to install tf2), so I can't really comment.
tf - mod for the original quake 1 game, first made. Also, there was a team fortress mod for quake 2, that never seemed to be as popular as the quake 1 version. Pretty sure the quake 2 mod was just called team fortress, same as the quake 1 version.
team fortress classic - originally a mod for half life, think they released a stand alone version of it a few years later though
tf2 - stand alone game, bundled with portal, among other games, with..what was it called, the orange box or something?
I'm sure arguments could be made, about which one is best. It would be a hard question to answer though, since the tech was so different between the 3 (4?) versions of the game. Direct comparisons would be a bit difficult.
My favorite will always be the quake 1, original mod though. I spent many years playing that version