Of COURSE he is important.
Consider how decidely non-Floydian "The Final Cut" sounded with his absence?
I would even go so far as to say that Rick's keyboard/synth playing is more integral to the sound of the band as a whole than even Dave's legendary guitar work.
This depends. Early Floyd, definitely yes. Floyd after Dark Side Of The Moon, not really. They could have had another Keyboardist come in and played the parts, he really wasn't very influential in the creation of most later songs.
Oh Yes I agree! Rick is 1 of the 4 parts, well 5 including syd of course! YES I think floyd is a 4 part band all equal in value of the "FLoyd" Sound! Oh yes rick is a master!
I think the question is wrong. In fact it should be: WAS Rick important for the PF sound. The answer would definitely be yes. Especially in the early days – say until perhaps Wish you were here. How would have sounded Us and them for example without Rick's solo? In fact it was his song in the beginning!
But most of all I like his improvisational sound on songs like Careful... or Main Theme.