I say Millie, DB, Maggie. Here is why.
I have ALWAYS gotten air on MF's 2 hills. But if someone ranks coasters based on airtime, then how is it that they enjoy Beast, TTD, and Raptor?
Millie has a gut wrenching first drop that has yet to be beaten by any coaster I've been on to date. Millie also has no trim brakes or MCBR to slow it down or ruin it. There is a reason why it's never dropped below #2 steel coaster on the planet in Amusement Today's polls since it's debut in 2000. When it broke down on ERT night last year, people were booing, cussing, and throwing trash outside the queue. I went during Halloweekends last year, and Millie's wait was posted at 3 hours. When the whole cable issue happened earlier this year, I heard several people declare that they were going to skip CoasterMania altogether if Millie wasn't going to be open.
People LOVE Millennium Force, and that is not going to change.
Diamondback ranks second for me because as much as I love the airtime, that grabby trim and the grabby MCBR just don't do it for me. If DB was trimless, it would be my #1 coaster, but we all know that will never happen.
Magnum ranks third for me. The lap bars hurt, and the ride is very rough in some seats, especially if you're unlucky enough to get a wheel seat. Don't get me wrong, I enjoy the ride and the air on the bunny hills, but a 20 year old Arrow hyper definitely has an ouch factor.