Which chess site has the most rapid players? It is common advise that a chess player trying to improve should limit their blitz chess. Online chess is filled with people playing blitz and bullet and I often have trouble finding players to play longer time controls. Is there a chess site with a lot of rapid players? I'm thinking that unfortunately, chess.com is the best option, but sometimes I feel like it takes too long to pair up, and the opposition is not so strong. I've heard that ICC isn't too good for long time controls either. Anyone have any information?
The vast majority of online chess games played on any site are played with very short time controls. Because of this fact, if you want to play longer games, you will have to wait longer, on average, than you would for a game shorter time control. 

If you are looking for quality chess games and you want relatively long time controls and decently high-rated players then you can try limiting your searches to high rated players.

You can select custom rating ranges on lichess and on ICC. This will allow you to, for example, filter out lower-rated opponents if you want a strong opponent. 



Another possibility is to play in the long-time-control tournaments that most popular chess sites have on a regular basis. Both ICC and lichess have regular tournaments with relatively long time control. The advantage of this is that once the tournament starts, usually the wait time between games is not that long.