Bleach is a sludgy mess, with 2-3 good tracks here and there. Nevermind has some good songwriting moments but it's marred by absolutely awful glitzed-out production. In Utero is a great album.
Really, the only reason why Nirvana was the band that broke alt-rock was that they were in the right place at the right time. Musically, they were never anywhere close to being the standout of the genre or anything. Compared to the stuff that bands like Sonic Youth and the Pixies were doing around that time, Bleach was an awful album. But Nirvana was the band that, for whatever reason, struck a chord with the record industry, so they were the first of those bands to get a marketing push.
Cobain himself said that Mudhoney should have been the ones to explode, not Nirvana. And if you listen to Nevermind and compare it to Mudhoney's album from 1991, he was right. At that point in history, Mudhoney was the far superior band. It may have been a different story in 1994, since In Utero is one fantastic album. But at that point they'd already become the biggest story in rock since the Ramones, so that's irrelevant.