For me, it'd probably be:
1. Shawn Michaels
He was just the complete package. He could be a brawler, he could be a technician, he could be a high-flier, he could sell, he could work a crowd, he could cut a fantastic promo, etc. He could do it all. He could wrestle a broomstick and it'd be a Match of the Year candidate. The greatest ever, imo.
2. Great Muta
The Japanese Undertaker. He, like HBK, could do it all in the ring (brawl, technical, high-flying, etc.), and had enough American appeal to win the World Heavyweight Championship in WCW. He is also one of the most decorated champions in Japanese pro wrestling history. And his gimmick was AMAZING. The most underrated wrestler ever, imo.
3. Ric Flair
He was Shawn Michaels before Shawn Michaels. He couldn't do the acrobatic manuevers that Shawn would be able to, but he was an even better crowd worker and an even better promo cutter. The guy just dripped charisma and was a real good mat wrestler. One of the greatest of all time.
4. Randy Savage
Another all around fantastic performer. A great in-ring talent who had the charisma to work a crowd like no other. OOOHHH YEEEEAAAHHH!!!
5. Bret Hart
Not the most interesting guy to ever lace up a pair of boots, but he is the definition of a technical wrestler. One of the best pure in-ring talents to ever get into the ring.
Honorable Mentions:
Hulk Hogan
The original superman of professional wrestling. He had the charisma, and was an underrated in-ring performer. He was never gonna be a great technical wrestler, but as a brawler, he could put on very memorable matches. WHATCHA GONNA DO, BROTHER?!?!
Sting
Yet another all around performer (see a pattern?) who had plenty of in-ring talent AND charisma. His Surfer gimmick was fun and nostalgic, but his Crow gimmick from 1996-1997 remains one of the best gimmicks ever in American professional wrestling.
Undertaker
One of the best gimmicks ever. Whether a heel or face, he could work a crowd. And his older matches with Bret Hart, Steve Austin, Mick Foley and Shawn Michaels back in the 90s were fantastic. Though he WAS slightly more charisma than ring work, his in-ring talent could not be denied.