Here's my take on it:
1. Size - Terrell Owens. Don't like the guy, but he's big.
2. Speed - Santana Moss. I wanted to pick Holt, but he has slowed down in the past two years due to that knee. Hopefully the surgery will get him back.
3. Release -
Torry Holt. This one is hard to look at unless you have a lot of film. Also looks more of an opinion, but Holt does get off the line just fine.
4. Route running - Isaac Bruce. Could have put Holt here, but Bruce has been doing some of the finest route running I've seen for years. He never had great speed (4.58 coming into the NFL), but his precise routes made up for that.
5. Hands -
Torry Holt. Enough said.
6. Body Control - Larry Fitzgerald. Amazing body control for a WR his size.
7. Cathing in Traffic - Steve Smith. No afraid to go after that football.
8. Yards After Catch -Anquan Boldin. He's a beast once he gets that football.
9. Ball possession - Anquan Boldin. I don't recall this guy fumbling, and that is pretty amazing for all the hits he takes trying to break tackles.
10. Blocking skills - Hines Ward. Made many blocks for the Steelers last year.
11. Heart/Character - Marvin Harrison. Never once did he complain about Peyton Manning choking in the playoffs all those years, and it eventually paid off as he finally got a Super Bowl ring. Can tell he loves the game.
This is just my opinion, and I'm sure that nobody will have the same list that I do, but that's good, it encourages debate.
On my list, the most anyone got was two (which re-states my point that no one WR is best at everything).
Torry Holt and Anquan Boldin are tied for my #1 NFL WR according to this method.