Cedar Point - (2007 was my last trip)
Millennium Force is definitely a great coaster IMO, it's #3 on my steel list if anyone cares.
Frankly, Cedar Point is a "bit" of a joke. I like the park for what it is, and it's still in my top 10 list of parks, but they have 5 or 6 coasters that are good, and the rest are mediocre at best.
IMO these are the coasters not to miss: Millenium Force, Raptor (Afterburn is better IMO though), Gemini, Magnum, Wicked Twister and Blue Streak.
The rest are meh. I'd take Vortex over the head-banging mess of Mantis, Mean Streak is a big pretty joke of a coaster, and well the rest are pretty much standard credits at best. And I'm a whore, but not so much that I got the 2 kiddie credits there. But still 15 credits ain't bad without them.
Notice that I left off Maverick on either list. It's not a bad coaster, IMO it's just not that great either. It jerked me around a lot and I don't like coasters like that. But it's still fun.
Kings Island - Or, my how the mighty have fallen
My last trip was 2005
Beast - Has been neutered, but would probably beat the crap out of you if it hadn't been. The tunnels are still a lot of fun, why the heck though are the lights on out on the course at night???
Top Deck

isn't nearly as good as Big Bad Wolf, but still a lot better than Iron Dragon at CP.
Son of Beast beat the crap out of me with the old trains, I can't imagine G trains making this a better ride.
Vortex - One of my favorite Arrow loopers, but I pretty much despise the genre now because of all the headbanging.
Flight of Fear - Maybe the best coaster in the park.
Tomb Raider - Not worth a long wait. It's VERY short.
Fire Hawk is going to be a lot like Borg..er Nighthawk, but I never got to ride it at Geagua Lake, but I've been on Batwing which is the same layout.
Racer was falling apart last time I was there. But I like the turnaround better on it than TR or Rebel Yell.
Frankly Kings Island isn't that great anymore. Go to Holiday World instead!

I know both parks have tons of credits, but IMO they've both lost a lot of what made them great. Coasters and otherwise. Neither is terrible as I've said, but ya know they just need to step it back up IMO.
*ducks the CP fanboys*