There's nothing wrong with a mixed reaction for the top heel. The nWo had a mixed reaction but they were still an excellent villain. All that matters is that most people hate him (easy to do, wrestling fans are fickle-- and I see the "let's go Cena" half flip flopping easier than the "Cena sucks" half) and that he's dominant and that he's fresh. It's not about creating a force that gets universally booed it's about creating a dominating heel presence that the WWE hasn't had in years, which is a big part of the reason their storylines have not been very compelling. If you look through all the great storylines you're going to find a dominating villain at the helm, and while guys like Kane and Mark Henry have looked strong as wrestlers at times, they haven't really controlled the landscape of the show like John Cena could.
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I tried to have a fierce rivalry with SuperNiceDog, but he made me look worse than a GameFAQs Contest!