Last year I convinced Duncan to go on MF with me. It's easily his favorite now.
I've never been on anything to compare.
Now, in defence of other coasters, however, there's more to it than just big hills and speed.
MF has that rare, smoothly flying experience. It's actually somewhat mellow. If you want something more exciting, then there are bumpy coasters, curvy-turny coasters, etc. One person's favorite may not be another's, for differing reasons.
One of the best things about MF and the new drag racer coaster is that Magnum's lines are usually no more than 10-15 minutes now, in the middle of the day even. ;-)
We go to Cedar Point in late September/early October, during their Halloweekends. Almost all of the rides are open, the weather is very pleasant, the rates are cheaper, the crowds are smaller, and they have extras like recitations of The Telltale Heart and haunted houses. Recommended.