Did you recently date your ex? If so I bet that relationship and how you interacted and felt are in your active conscious. That's part of why being single for awhile can be nice rather than starting a relationship a week or month later.
Maybe you just compared him to your ex because your ex is what you're use to. It's also possible you think your ex is really special and don't like the new guy as much.
Most Helpful Girl
I feel you. Doing that as well. It is because, maybe deep down inside, I do know for sure that this ex is the most compatible with me. I keep comparing the new guy with him. I hate this for sure but can't do anything about it, until I get someone so much better than him.. I guess