James Gandolfini, The Sopranos. I remember watching that show pretty much every Sunday. I can't think of a better actor, he pretty much owned that role and hit every note and range of emotion. Plus, I might be a bit biased because he is also from Jersey, and he also helped out the Wounded Warrior's Project, which I also support and think are just great. But I really think that he might have given the all-time GREATEST performance in any television series ever! I also hear that Martin Sheen was fantastic in The West Wing as well.
I love The Sopranos but I don't really think of it as a 90s show. I'd probably choose David Duchovney as Fox Mulder or Gillian Anderson as Dana Scully.
Or maybe Mark Hamill as the Joker from Batman TAS?
Ed O'Neill as Al Bundy would be on the list for me.