I'll just go through each sport. Feel free to post your own lists.
MLB
5.Roy Halladay-Fearless pitcher.
4.Johan Satana
3.Mariano Rivera-Last season was one of his best.
2.Albert Pujols
1.Manny Ramirez-I hate how he plays the game, but I don't want to pitch to him in a big spot.
NFL
5.Ed Reed-All over the field
4.DeMarcus Ware
3.Adrian Peterson
2.Brian Westbrook-I pray he doesn't take a screen pass 70 yards.
1.Peyton Manning-I know he's gotten flack for some playoff losses. But he's still the best.
NBA
5.Paul Pierce-In the final two minutes, he takes over.
4.Chris Paul
3.Dewayne Wade
2.Kobe Bryant
1.Lebron James-He's done more then Kobe and with a lot less.
NHL
5.Mario Lemieux-Even if he came back, I still don't want to see him
4.Evgeni Malkin
3.Jarome Iginla
2.Sidney Crosby
1.Alex Ovechkin-How was he not an All-Star starter?
Soccer
5.Emmanuel Adebayor-He could probably play RB in the NFL.
4.Robinho-Has really taken his game to the next level.
3.Steven Gerrard
2.Fernando Torres
1.Cristiano Ronaldo-Yes, make that 5 Premier League players. But its the only league I watch. Who would not pick Ronaldo?