One of two things happen when you break up with someone - you either forget about the good things or forget about the bad things. You have clearly forgotten about the bad things. And this willing forgetfulness makes you consider getting back together with someone that was a habitual liar and woefully immature.
Getting back together with this person, regardless of whether or not he promised to change, means that you'd have to give up a guy "who is everything [you] wanted." So, apparently, this means that you'd prefer a guy with clear shortcomings to a guy that is essentially perfect. Sounds like a really dumb thing to do if you ask me.
Don't date a guy based on potential. Date a guy based on who he is. The guy you have now is apparently a great one. Don't screw that up for someone that is trying to scrape all the bad off himself.