cod3 has no multiplayer but is an EXCELLENT single player game.
medal of honor is garbage put out by EA. It's cookie cutter, no frills single player and bland multiplayer.
The question is. Would you like a great single player game with average replay value, or would you rather have a below average single and multiplayer game with some replay value, but you won't ever really want to play it again.
Go with COD it's a much better game.