I've been to most of the parks in USA, except Lagoon. My count is 425 coasters.

If traveling from abroad, I think you need to establish how many "other things" you want to do and how long you are wanting this adventure to last. Cedar Point is my personal favorite, as Millennium Force, Maverick, and Steel Vengeance are absolutely amazing. For me, the top four parks are Cedar Point, Magic Mountain, Islands of Adventure, and Busch Gardens Williamsburg.

Best Single City/State Trips:

1. LA - Magic Mountain, Knotts Berry Farm, Universal Studios, Disneyland, Seaworld San Diego.
2. Orlando - Universal Studios and IOA, Seaworld Orlando, Bush Gardens Tampa, Fun Spot Kissimmee, Fun Spot Orlando, and Disney World.
3. New York City - Much more driving but you could realistically do Six Flags Great Adventure and New England, Lake Compounce, Coney Island (Luna Park), Rye Playland only if you have extra time. I put this on here not for the coasters, but because you can experience NYC while also hitting some good coasters.

Best USA Crazy Road Trips:

1. Chicago to New York City: You can get Six Flags Great America, Cedar Point, maybe holiday world, maybe kings island, anything in PA that others have mentioned (Knoebles is the must), ending with New York City area.
2. New York City - South on I95 to Charlotte or on to Atlanta: You could do Six Flags Great Adventure, Kings Dominion, Busch Gardens Williamsburg (the gem here), Carowinds (Awesome collection), maybe dollywood, maybe six flags Georgia.