If you want an MMA game with replay value...pick up PrideFC's game for PS2. It has a deeper roster than Sudden Impact, better entrances, better arenas.....all that stuff - and my favorite aspect of the game: you CAN actually work through submissions attempts! You don't INSTANTLY tap when you get caught in a submission. You have a small window to reverse the hold, or just press your reverse buttons as you see your opponent deepen the submission - to hold the idle position, and not have to tap. Just my thoughts though.
I own everyone on PrideFC with Royce & Antonio Rodrigo Nogueira. Don't go to the ground with me!