Notice how high rated players win most of their games, and upsets are rare. If this translated to the real world, I'd expect the strongest crazyhouse human player at 3 0 to beat everyone else in the world in most of their games. This is what I mean by the skill gap being much larger in crazyhouse than in normal chess.
Contrast that to this (4 2):
This one looks normal, what you'd expect to see in a chess tournament. It seems what I'm talking about doesn't apply if there's increment happening, so I hold increment is a must for crazyhouse for it to have any professional future. At least, nowadays the no increment tourney seems to have as much interest as the inc tourney, so over the years people have gotten used to it. This would break my claims so they'd only apply to players that do 3 0 or faster exclusively.
(to recapitulate: my claim is that in the 3 0 tourney, that 2300 player that won by a landslide would have won against the same people at 5 0 or 10 0, so if the winner is going to be the same it doesn't make sense to use longer time controls, and that's why they're so rare)
The ICC, FICS and chess.com all have specific Crazyhouse ratings. There's also other places where you can play them at correspondence time controls (say, 2 days per move) and they have specific ratings, such as in brainking.com (which calls it "Loop Chess" because promoted pawns keep their rank when captured), Scheming Mind, or chessvariants.com (which also has "Chessgi" in where you can drop pawns on the first rank.)