I have played plenty of online multi players, again I will say not one has ever come close to perfect. whether it is faults in network code, latency, game/environment bugs or simply gameplay/balance issues I am not aware of any that come close, if anything multi player is much much harder to be fault free.
10/10 doesn't mean perfect just to be clear. It's about the fun factor. Point about multiplayer still stands. On leaderboards certain people have put in 1000s of hours on one game! If anyone has put in 1000+ hrs on any single player I'd be amazed.