In my opinion the word 'better' is meant in the context of loa to mean 'have a better connection with'. So your ex might look like Angelina Jolie or Brad Pitt (which mine actually does lol but anyways) and have really great traits (plus flaws obviously) and you're pining after them, but then this average looking person comes along who can make you laugh harder than the first person, maybe they actually get you in a way that you sort of wished the other person did, maybe they make you feel that bit more special, maybe they make you feel more relaxed, maybe they're more open to things the other person wasn't...maybe they unlock a side of you that the other person didn't. They're uglier and have their flaws, but somehow, the relationship seems really natural and then all of a sudden you start to enjoy being with this other person a lot....and then you start to think, actually, this isn't half bad. 

A film that really shows this is 'Forgetting Sarah Marshall' I advise you all watch it, he gets his ex back in it but there's a twist and Russell Brand and Mila Kunis are in it. That's a movie that really shows how we put people on these huge pedestals due to what we think of them or the time we spent with them, when maybe we over look someone who fits us way more.