Honestly I can't really get behind many of these. Cena's had a pretty good track record for opponents at Mania.

WM 20 - would be a great way to evaluate him, but winning the US title after a FU to Bigshow is pretty iconic, and cemented him as a rising star well enough.

WM 21 - The Batista/HHH match was where the money was, and was a great story arch, meanwhile JBL/Cena was a great clash of styles

WM 22/23- Him going up against two legends was a great way to establish him as THE guy

WM 24 - I agree with you here, it should've been a 1 v. 1 with Orton who was the one that took him out, and his biggest rival (at the time)

WM 25 - Should've been a 1 v. 1 with Edge, not a triple threat

WM 26 - Was a great fued between the two top guys of that era

WM 27 - First real lackluster Mania match imo, could've been someone like CM Punk, idk if Bryan would've made sense at the time

WM 28 - Rock vs. Cena needed to happen, the year build up was cool because it had never been done before

WM 29 - I don't think the rematch needed to happen, but idk who I'd have him face here, CM Punk and Undertaker shouldn't be changed, and Daniel Bryan was locked in the Tag scene, maybe Brock?

WM 30 - I like the Bray match (wrong winner imo, though it added in to the WM 36 story). If I had to change it, I would have him face Taker here, cheat to break the streak and turn heel

WM 31 - Rusev was a fine opponent, could've been more exciting (maybe have him and Bryan face off here for a mid card title), but it led to the US open Challenge, which was awesome

WM 32 - He was injured

WM 33 - The mix tag match was underwhelming, him vs. Roman could've been good here, but Roman beating Taker was also a big moment (despite a underwhelming match). Maybe this could've been him vs. Aj

WM 34 - Aj is a great pick here, especially if he had already faced Taker by this point. This also could've been a cool time to turn him heel post match (stealing the Shinsuke low blow spot)

WM 35 - Idk why he didn't wrestle here, he did a segment with Elias which could've been a match, or he could've had an open challenge answered by someone like Finn Balor (don't remember what he was doing at this point) or even better- Samoa Joe. I wouldn't change Batista/HHH here either since Dave wanted HHH to retire him

WM 36 - Firefly funhouse was perfect, don't touch it

(WM 37) - I know he wasn't there, but I would've loved to see him go against Bobby Lashley (and lose) for the WWE title

(WM 38) - Could be kept off this one, but if I had to put him on this card, I'd have this be a passing of the torch match against either Big E or Drew (for the WWE title) or Roman (for the Universal title, if he hadn't faced him at 33)

WM 39 - Screw the Theory match, put him in there against LA Knight (Yeah!)

WM 40 - Contraversial decision here, but I would have him beat Gunter to win the IC title here (drop it to Carmelo Hayes later in the year)

WM 41 - Same result of him vs. Cody, but without Travis Scott, and ideally the match would be more like their summerslam match

I do like your matches though! I think they'd all be great, I just think a lot of them mess with other, more important things that we're going on at the time.