The only one worth repeated re-watching you mean? The other 3 you can keep in the archives... I'm not saying this to be confrontational, but the other last 3 aren't classic like First Blood is. Not by a long shot!
I think RAMBO could hold up as a lone film in its quality, storywise you need the past of the character to understand where he's at, but it was a well made film, but definitely First Blood is the best film as far as being able to exist alone and stand the test of time; FB2 and Rambo 3 are fun but as individual films they'd just be macho action flicks.