08's team was the best Celtics team of the run and it's not close - that was the best team the NBA has had since the 05 Spurs. Until KG's injury, 2009's team was right there too because improvement by Rondo and Perk, Baby's emergence as an actual NBA player and better chemistry among the starting five made up for the diminished bench. It's easy to forget but Garnett was a top-5 player in the league those two seasons until his knee gave out. That makes a huge difference. If that injury hadn't happened, they would've cruised through the playoffs easier than they did in 2008.
I would agree last year's team was better than 2010 barring injuries. Hard to compare to this year, though, considering KG was just not as good last year as he was/is this year and he's always been the lynchpin to this team. KG should've been 2nd Team All-NBA and First Team All-Defensive this year. His best season since the injury.
I'd also argue this year's team was on the whole harder hit by injury than last year's, but last year had by far the most impactful injury with Rondo's elbow dislocation. That knocked them out of the playoffs. Not to say they would've won rings if he hadn't been hurt, as they were still down 2-1, and beating Miami only would have put them in the Conference Finals facing a Chicago team that seemed to have Boston's number. Otherwise, though, Shaq and Jermaine got hurt, but that's predictable. And Perk was out to start the year but was fine by midseason, so he didn't miss anything that mattered. Rondo had some nagging injuries last year, but also did for stretches this year. This year added a significant injury to Ray, season-ending injuries to Green, Bradley, Wilcox and O'Neal, lesser but still impactful injuries to Pierce and Pietrus (he's not close to 100%). They simply had better depth this year. And got luckier with Rose and Howard going down taking out Chicago, pushing Orlando from 3 to 6 and thus knocking Indiana out of our bracket. If those two guys were healthy, the Celtics would've had a path of Indiana-Chicago instead of Atlanta-Philly.