I have 4 big favorites on the old DC.
Power Stone, a fighting game that explores a 4-player smashing brawl, before Super Smash Bros. Even having it's own version of the smash Ball with the literal Power Stones and each fighter having their own special powerful SMASH or POWERSTONE Form.
*sigh* I am going to killed for this pick, Sonic Shuffle. Before I get killed for this one, HERE ME OUT! Besides it being a Party game and a sour-ish story, the game is still fun across multiplayer, you had you own VMU to check your own cards for movement and combat secret. The game boards we're inventive, changing and the minigames we're a lot of fun along with the events.
Skies of Arcadia, SKY PIRATES AND AIR SHIP BATTLES, NOUGH SAID!
Sonic Adventure 2, TONS OF FUN!