Rock album? More like hip-hop with guitars playing over it. I've heard more rock from Gnarls Barkley and Lupe Fiasco.
Emo? Sure, "Prom Queen" is undoubtedly crappy for Lil' Wayne's unnecessary eagerness to tack his heart to his sleeve, but the rest of The Rebirth, to Wayne's credit, experiments with multiple facets of rock music, whether it be through the No Doubt spunk of "Get A Life" or the tom-heavy funk of "Ground Zero".
Worst album of the year? Hardly. The Rebirth is by no means a masterpiece, but I've heard much worse. Despite nearly an all-out refusal to spit more than two good verses ON HIS OWN ALBUM, Wayne's newest is kept afloat by beats that can range from the interesting to replay-worthy. Take "Knockout" for example. Wayne's verses are adequate at best, but that Blink-182-style guitar line and that scene-stealing turn from Nikki Minaj make for a song that's significantly better than decent.
So everything you've been told about The Rebirth is wrong. It's listenable, and, considering how much crappy press it's gotten since its release, it might just exceed your expectations. That said, The Rebirth isn't really worth your money. Buy "Knockout" and maybe "On Fire" and call it a day, because there are far too many times when The Rebirth lives up to its anti-hype, such as every ballad and whenever Lil' Wayne mixes his Auto-Tune with his distortion. "The Price is Wrong", in fact, could be the worst song of the year. It's all pretty much a misstep, but it won't disgust you quite as much as people would have you believe.