No doubt this one has to go to WM23 V HBK. That match still rules, in my opinion. HBK carried the match I think to the standard a few people talk about it (myself included). But this match had everything going into the hype - great hype of the friendship & rivalry between HBK/Cena, the 'big time player' HBK taking on the 'new kid', "old school V new school" angle were all run greatly!
the match did not let down either - again HBK carrying a majority of this. He brought his a-game hype and ability. it had everything too: counters, sneak pins, submission, kicking out of finishers, a referee down, steel stair spike piledriver! Everything in this match was awesome, and knowing that Cena didn't sell the leg injury well, and how pissed HBK was just topped it off for me.
Cena V JBL - shocking. good build up to it, but a poor match. didn't do anything for Cena as such, the match, didn't build him up. 10 minutes of jbl beating him down and then he gets the shock win. woo, great.
Cean V HHH - close runner up! the hype was done poorly, but was still there. this one's second due to the sheer fact that Cena was set as a super-human, and Trips was 'i want the title back, and im gunna fuck Steph to get it'. big upset, and in general a great match which really pulled the crowd in.
cena v show - typical WM opening match. Again, similar to Cena/JBL but with a lesser title on the line. good though, for building his mid-card status.
cena V HHH V RKO - Great match, but still has nothing on Cena/HHH or Cena/HBK. I really only remember Orton dominating this match. Cena has his little bits, here and there, but nothing flash. more likely this would happen, when you've got two top tier guys to contend with...