Your first step is to let yourself grieve at your loss, and get over you ex. this takes time, and you are making a mistake to start dating before this is complete.
if you start too soon, then you are correct, you WILL be comparing the guys you meet with your ex. And this is a no-win situation. Every guy you meet will either not be up to your perceived standard (based on what you ex didn't do right), or will be too much like your ex (in the things he did wrong). It is too soon for you to see the real "middle ground".
What is worse is that you will come off as a "bi-otch" because of it. Not because you are, but because you are as yet unable to accept a decent guy for what he is -- flawed. NO ONE is perfect. But right now your perception of "perfection" is twisted due to the internally unresolved conflicts with your ex.
The ONLY way out of this is time. Maybe counseling, but time for sure. You NEED to learn to accept and live with yourself. You are NOT "damaged goods", but you've still got some time to go before you will fully realize what a treasure you really are. And until that happens, you will not be able to convince a single male what a "catch" you would be.
So forget dating for a couple of years (this is about how long it take to "heal" after long-term relationship or divorce). Go out with friends from work, or family, but forget any "serious" relationship with the opposite sex. (refuse blind dates or offers to "fix you up") If you have FRIENDS that happen to be male, fine, but forget "dating". Learn to live with YOU, and learn that you are not as bad as the ex might want you to believe.
You ALSO need to learn that HE is not as bad as you used to believe, and probably still believe at some level. ONLY THEN will you be able to accept another man as a potential serious date, and potential serious "mate".