I think that he was in love with Cassie while they were together, and I think he will always feel something towards her.
Lisa was originally a one night stand. But after Dean found out about Ben he started to think about how he wants to have a family before he dies. He sees Lisa and Ben as the perfect opportunity to create that family. Plus I think he really cares about them and could possibly love.

So you think he loves Cassie more?

Cassie

100 %

I think he loved each of them when he was with them, but neither of them now.

def lisa, watch "99 Problems", said if he could have a normal life and be happy it would be with her and ben. and he dreamed of her!