Play Mario Kart DS using local DS-to-DS mutliplayer. It's crazy good. There have been nights where we've played for an hour or two without even realizing it.
Now play Mario Kart DS using online multiplayer. It's alright if you're looking for a challenge but it gets old pretty fast.

Voice-chat wont make it exactly like playing locally but without it there's no real social aspect and the game ends up feeling distant.