(All answers from my generation)
Kind of a loaded topic.
In terms of popularity:
1. Stone Cold Steve Austin
2. The Rock
3. Hulk Hogan
4. John Cena
5. The Undertaker
In terms of storyline (who writers across multiple companies make most "powerful" in-ring):
...kind of a toss-up between Undertaker, Rock, Austin, Goldberg, and Lesnar. Cena, Ultimate Warrior, Hogan, and (sadly) Triple H are not far away.
In terms of flat-out in-ring ability (ability to have a great match):
1. Chris Benoit
2. Kurt Angle
3. Shawn Michaels
4. Bret Hart
5-8. Edge/Rob Van Dam/Rey Mysterio/Chris Jericho
*somewhere down this list- top 2 in-ring "big guys" - The Undertaker and Brock Lesnar
In terms of microphone:
1. The Rock - great heel, great face
2. Chris Jericho - great heel, great face
3. Shawn Michaels - great heel, great face
4. Stone Cold Steve Austin - best babyface of all-time, underrated as a heel
5. Vince McMahon (not really a wrestler, but deserves to be on list) - best heel of all-time
6. Ric Flair
7. Edge
8. CM Punk - overrated as a face, but great heel
9. Kurt Angle
10. John Cena
overall (in my opinion):
1. The Rock
2. Stone Cold Steve Austin
3. The Undertaker
4. Kurt Angle
5. Edge
Most overrated:
1. Triple H
2. Triple H
3. Triple H
4. Triple H
5. Did I mention Triple H?
***honorable mention for practically every category:
Sting