Though my first fighting game was from Capcom, Street Fighter 2 Turbo, my tastes have changed.
I think Namco has more strategy and more moves, so I will stick to their games. My favorite series is Soul Calibur, more specifically, II on the cube. It looks great, plays great, sounds great and has lots of content. There is lots of strategies to be found in this game. Tekken is ok, but I don't like how strafing is done in the game.
Capcom games seem confusing with 6 buttons to use. In arcades, I can hardly tell what is going on when I watch people playing.
SNK games are rare, but I like their simple approach.
The only Sega fighting game that I know of is Guilty Gear XX. I have never played this game, but my friend said it's a great game.
As for Mortal Kombat... Well, I'm not too sure I like the changes. It feels slow and sluggish compared to the other fighters.
I barely play them, so i really dont know much about them. Just the ones (Like powerful said) that require a bit of strategy, and not just pressing random buttons... Those annoy me...
i liked soul caliber 2 for xbox more. for one thing it actually runs slightly faster, i also felt that link was a bit unbalanced. hey, you also forgot to add nintendo in there for supersmash bros, ok not your traditional fighter game but it still falls in the category.