Strikeforce really only had a 3 or 4 year run where they were a big time promotion but they they really put on some good fights in that time frame.PRIDE
WEC
Strikeforce
Bellator
Dream
Although, IMO, it wont be long before Bellator surpasses Strikeforce. Nostalgia is a hell of a thing, I do believe most of us have an idealized version of Strikeforce.