The best fighting game of all time is Marvel vs Capcom 2 made for the dreamcast. There is no other 2D fighting game that is a good as MVC2. The game is currently being in HD for the PS3 and the X360. As for 3D fighting the best ever made would probably be either Soul Calibur 1 for the Dreamcast or Tekken 3 for the PS3. But if u want to get the latest and greatest fighting games, you should definately consider:

Tekken 6
Soul Calibur IV
King of Fighters XII
Street Fighter IV

Hope that helped.

Peace.