Though, in my opinion the best neoclassical albums are Vinnie Moore's "Timy Odyssey" and "Mind's Eye". With Tony Macalpine's "Edge Of Insanity" coming in a very close second. David Chastain's neoclassical albums are also very very good.
So, if it was me and I were to buy just one it would be Mind's Eye, but all of the ones I mentioned are very good.
If you want to listen to something a little newer, you should definitely give George Bellas a listen.