First off, Colonel Tom Parker was a cold-hearted bastard. When told of Elvis' death, he said something to the effect of "Nothing has changed. I'll still get my 50 percent.". Nice to know Elvis was managed by such an insensitive turd.
Secondly, his life was really screwed up from the sound of it. Yes, he was a great entertainer, a singer whose music will live on for a long time. Outside of performing though, he was really, really messed up.