Modric is what, 4 years younger than Arshavin? Why are people comparing them? Arshavin is in his peak and is pretty much fully developed now. Modric is still only 23 and getting better. We'll see where he is at 27. Besides, they're totally different types of player.
I don't know why people are comparing them, they don't even play in the same position.
Arshy is better though, Modric is out of his depth.