You have to tred carefully with Dion. Remember he had to turn out hits so there are a lot of not so good ballads and so so pop stuff. If you want to stop playing record roulette, track down Everything You Always Wanted to Hear by Dion & the Belmonts. It is a best of that Laurie put out. It has the good hits, some good mior hits and a few obscure cuts. It is probably the most solid of the collections. Other than that it is slogging through a bunch of 45s and the albums, which have some good filler tracks on them. Like a lot of pop stars, he is a guy that could be well served by someone like Rhino or Ace compiling a solid critical collection of his stuff. There is one great CD there.
Another 50s guy overlooked by Americans is Del Shannon. The Brits have always championed him, pretty much adopted him after his late 50s/early 60 carreer in the states died. There are so many rit reissues and best of collections of his stuff, including a very nice series of 7"s that came out during the rocakbilly revival in the 80s. A lot of it is pretty easy to find, much easier than finding the original singles here. One of the best ofs that I have that is pretty good is Runaway Hits! Listen to him and you can hear the influence on bands like the Boys.
Another guy I like who I am gonna blog soon is Troy Shondell. A bit more on the pop side but he had a very good voice and used some odd/stupid voice inflections & tricks. He was hugely influential on Tommy James who named his backing band after Shondell.