No doubt for me that Scholes is a higher breed of player than Gerrard in relation to the central midfield position but I do think Gerrard purely for his 2005 CL exploits elevated himself into that world-class bracket. Furthermore having watched him live, I was so impressed at how good a player he was (during 08/09) in that roaming role where he wasn't responsible for dictating the tempo in deeper areas. Keane on the other hand is very underrated technically and also in terms of movement off the ball, he was brilliant at retaining possession and constantly moving to support the man on the ball, something we greatly lack in midfield today. As a three man midfield, with them all at their peak.. it'd make a fantastic trio.
Keane Scholes
Gerrard
I'd say probably for pure class Scholes comes out on top, impact on big games and effectiveness goes to Keane and Gerrard for his completeness (he could tackle, head, take set pieces, long distance goals, through balls, switch the play etc) and it has to be admitted that he never played for a top side or a top manager, nor did he get to play for a three man midfield often enough which probably would've brought the best out of him. The other two trumped him in centre midfield I think that is pretty much clear but in a free role, it is a toss up between a young Scholes and Gerrard at his peak.
Sad to see people rush to call him mediocre because he is definitely not that and is/was a world class talent in my opinion... these three players are easily the best central/attacking midfielders the British & Irish Isles has produced in the past 20 years.