Let me correct a few things from the OP. One there was no briefcase shot to the head to Cena. I have the DVD, he hit Flair with it, not Cena. cena was busted open from the Eliminationm Chamber, and Edge laying in punches.
Two, you can't remember Cena losing cleanly in the pat 5 years? How about when HHH beat him in possibly his "last match" on Raw before his Iron Man Match at Bragging Rights 2009? What about Orton in Hell in A Cell 2009? How about when HHH beat him at NOC 2008? How about when Batista beat him, clean, at Summerslam 2007? If you dont want a bigger star example, JBL beat him in NYC parking lot at the Great American Bash, 2007? I know HHH and Batista are/were "top stars", but you said you couldnt remember him ever losing cleanly. JBL certainly wasn't anymore, if he ever was. I could think of more, but I figured Id just jog your memory a little bit.
Anyway, how are you to be considered a "top star" if you're losing "more often" in clean fashion? You brought up MMA, UFC, and amateur wrestling. That shit's real, last time I checked!
I think there comes a time, and you brought up a valid point, that if you want to make new stars, the top guys have to put them over. Cena has put Sheamus over to the extent that he's NEVER BEATEN HIM. You dont think that fact has helped get him over? I think his victories over Cena have been what has gotten Sheamus over as a heel. It doesn't matter that his victories have been somewhat tainted, the fact is, he's beaten him over and over again. If they want to make a top face, then yes. a top star needs to beat them. But to make a top heel, Id argue that by them "cheating to win" in big matches, it gets them over even more as a HEEL. So sure, if theyre serious about pushing Morrison, put him over a top guy(not your champ) clean. But the idea that top stars never get pinned or have to get pinned cleanly is rediculous.
Finally, why is thism directed just as Cena? Its just as much apart of his gimmick that it is The Undertaker's not to lose cleanly. Can you remember Taker losing clean other then to Kane last month at NOC in the last 5 years? That was even "excused" on Taker still being weak from his "vegetative state". You pick on Cena for being true to hios gimmick, which I personally like, while a guy like Taker NEVER loses cleanly, which I dont mind either. Its part of their gimmick man. Further, its what makes them "top stars" in the first place.