Geez.... the first one is terrible in a great way. Sure it's got the low budget "cool factor", and has a more surrealistic horror to it, but that girl is screaming thru nearly the whole movie... Anyways, it's great as an "artsy horror flick", but not much more.
Texas Chainsaw Massacre II was the best, IMO. Had lots of humor, and was more like a real movie, with lots of fabulous one liners, "incoming mail", one I'll always remember... It was kinda campy like Evil Dead II or Return of the Living Dead.
I don't think any of the other sequels were any good.