The best teams are almost always those with the most star power. If you have two or three guys on your roster who are exceptional, you have a great chance of advancing far in the playoffs. If you only have one player who is very good, things are much tougher - no matter how "deep" a roster you have.
Interestingly Dallas won it all last year with only one fantastic player, completely defying the last paragraph. It was a hell of a thing. Just don't expect it to happen again anytime soon.
Last year's abberation mainly happened because Nowitzki was the best player in the world during the playoffs, LeBron choked terribly in the Finals, and Miami's chemistry floundered. This is taking nothing away from Dallas - they deserved to win and it was incredibly fulfilling watching them do so - but last year's Finals was really more about Miami's stunning failures as opposed to Dallas' fantastic team play.
This year will not be like last year - unless the Celtics somehow conjure up some insane Ubuntu magic, which seems very unlikely. This year will be back to normal.
We have an unusually large amount of top-loaded rosters this year. Miami, OKC, San Antonio, the Lakers, and the Clippers are all very star-heavy. Not coincidentally they are the favorites (probably in the order I just wrote.)
Here, according to baskeball-reference.com, are the star players on each remaining playoff team with PERs above 20 during the regular season. It's a very top-heavy year.
Miami: James 30.7, Wade 26.3
OKC: Durant 26.2, Westbrook 22.9, Harden 21.1
SAS: Ginobili 24.1, Duncan 22.5 , Parker 22.0 (Splitter & Mills also have high PERs in limited minutes, but we can't consider them important enough to put in this select company.)
Lakers: Bynum 22.9, Bryant 21.9, Gasol 20.5
Clippers: Paul 27.0, Griffin 23.4
Boston: Garnett 20.4
Philly: Lou Williams 20.2
Indy: no players above 20 PER
There are some very high numbers there. No offense to last year's Dallas team, but I doubt they would have made it through the West this year.