Just play Mario Kart Wii online. It's so much better. Oh and did I mention there's NO LAG?
I'm tired of this misconception.
All games have lag regardless. It's just that games like FPS, racers, and turn-based games all have ways to hide lag. FPS and racers make it so the peers are seeing a basically CPU-mirror of the actions of the other players (but internally keeps track of the real positioning to avoid desync).
This is why in Mario Kart DS, sometimes Snakers would appear spastic as the CPU cannot replicate the actions fast enough to other peers, or when a person disconnects from a FPS, he runs in a linear path from his last movement option as the CPU is predicting and displaying its predictions on where he will move.
Turn-base games can really ignore lag disregarding response time since the game either keeps track of move usage, HP, magic usage, or positioning and just needs to retrace back to the peer. Movement is usually linear (if there's any), and if not, the end path is always the same.
Fighters do not have that luxury. Hiding lag would be awful. If the CPU mispredicts, you may think you've hit the opponent, when in reality they are actually a few spaces away. Also, quick movement like foxtrotting and dashdancing may lead to the abuse of a prediction system that's already flawed in design. Fighting games is about precision. A system that has the possibility of mirroring positioning incorrectly is out of the question.
We're asking for the impossible here. Fighters online are always the most noticeably laggy. Even in other fighting game communities, they'll complain about lag. It's a flaw with the genre.
It's only made worst by how Nintendo handles their online. But that's not the only factor. Stop comparing Smash to Mario Kart, they're not even the same thing. <_<
Everyone should read this before they whine.