I would have great difficulty choosing only one or two players. The "1989" was magnificent, I've never seen better (except maybe 182 Aussies).... the "1975-1980" Widnes team was full of talent too. I only go back to the 60's so can't really say too much about anything beyond that.
But to pick just two players:
Denis O'Neill in his young days was the best. He could do what JD did in his day - but was even quicker (I think). He seemed to me to be the same as an Offiah - give him the ball in the clear and you'd never catch him. He could have been one of the best ever players in the world, but for "Murphy's elbow" (I know people argue it wasn't him... but to us it was always him).
Ian Hare For reasons unknown to me, he didn't seem to play many games but was the first winger I remember playing for Widnes that had real pace to burn. From memory he knew where the line was and could do a spectacular dive in the corner to finish off a move. Played for GB once I think, maybe twice, but we never got players in the GB side in those days. It was all Leeds, Saints, Wigan with a smattering of players from other clubs.... actually pretty much like it is today!

So so hard choosing just two.