See the difference is I think everyone who gets crushed by Cena will benefit just by virtue of being involved in a storyline where people really want to see them win even if they don't, with the amount of build they get to take him down being the most important thing rather than the result.
Now I agree that the one who finally beats Cena should be thought of in advance, but that's so the ultimate victor can be properly built (since the guy who takes him down needs a bigger build for the story to flow well) before the storyline gets stale more than necessarily needing to have someone beat him to get fanfare. The guy who gets the biggest build will get more "over" than anyone who went against Cena regardless of whether he wins. It's just that if Cena isn't ultimately beaten the story doesn't get a good resolution, overstays its welcome like the nWo did, and then people tune out.
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I tried to have a fierce rivalry with SuperNiceDog, but he made me look worse than a GameFAQs Contest!