I think the problem most people have when they try to learn other peoples solo's is that they dive in over their heads, get frustrated, say I can't do this and never try again. Like anything else you have to train yourself. Imagine going to the gym for the 1st time, you wouldn't (or shouldn't) put 2oolbs on the bench press, or run 2 miles, or workout for an hour and a half, you would start off easy and work your way up, as you got more fit you would take on greater challenges.
Forget trying to learn Iron Maiden the ist time out of the ring, start w/something basic like a Beatles or Chuck Berry or Eric Clapton solo and work your way up to it. It's tough trying to capture someone else's phrasing and emotion on your instrument, but don't give up, just figure out a plan of how your going to get where you wanna be.