This is an interesting question; not so much the specific question of who is better this guy or Curry, but rather the more general question of just how good is Steph Curry as compared to anyone in the history of the game.
Even though Curry puts up staggering numbers, I think his contribution is actually under-rated. I think the player that I compare him to the most is Steve Nash; better than Nash, but similar.
When Curry has the ball, the entire defense has to focus on him. He dictates everything; switches, sags, all the defensive strategy. He can beat anyone off the dribble so you can't overplay or try to force him in one direction. His court awareness and passing is right their with anyone, and then his shooting is off the charts both in terms of quick release and accuracy. Nash was that same way.
I also really like that many sequences that start with Curry, end in an assist but after 2 or 3 passes. There is a team mentality that contributes to this but it often starts with Curry knowing to get the ball moving instead of dribbling around or shooting.
It is a cliché but Curry makes everyone around him better to a greater degree than anyone else in the league. This is resulting in the team winning more than any team in history even though the team may not have all the future hall of famers like say the Magic Lakers, Jordan Bulls, or Bird Celtics.
To the original question, I don't think Lillard is close. Plenty of players have scored 50 points in this league (everyone remember Tony Delk?). I think Lillard is great and he may continue to improve but for now, Curry is in a stratosphere all his own.