Actually, winning almost every time is how you build a top guy. To take one WrassleGAF favorite, winning all the time is how Mark Henry went for midcard joke to the biggest monster heel in recent years in WWE not named Brock Lesnar.
There's a reason why the fans react to certain people as stars (Cena, Orton, etc.). They win all the time. Punk didn't become a made men as a top guy 'til he held the title for almost a year.
You have to be careful with how you job a top guy. Cena just jobbed to Bryan. Jobbing him to Sandow, right after he came back, would've devalued Bryan's win. Now, I'm not saying Cena shouldn't ever lose, but yes, he should win the vast majority of the time. Becuase that's what worked in the Bruno era, in the Hogan era, in the Austin era, and yes, in the Cena era. The problem isn't that Cena wins all the time. The problem is that their are shitty stories surrounding Cena winning all the time.