Yes, there are other super-fast characters in comicdom, but the iconic speedsters are absolutely the Flash and Superman. There have been multiple stories in which they raced to see who is faster. Hypborea.org chronicles them all.
The answers of course has to be the Flash (take your pick which one, but I would choose the Silver Age version, Barry Allen). Yes, classic Superman is fast enough to turn back time, but the rebooted version in DC's New 52 has been powered down so that vindicates the Flash as the fastest superhero even more.
Now that we've resolved that, I need to help my nephews answer the question of who the strongest superhero of all time is -- and the answer of course is the Hulk. Carry on.