Here's some information you might find shocking: there are women out there that are probably better looking then your wife. There are probably some women out there who might even be better for you. Here's the thing though: that doesn't matter.
See you've made a promise and being a real man in the relationship you're in revolves around you maintaining that promise. Of course you're going to have attractions to other women or think how hot other women might be, but you made an oath to someone that should supersede any basic physical attraction that you might have. It does get easier if you work on growing stronger in your relationship with your wife. Remember, you chose her above all others on her merits.
A couple of good books that help in this area are The Five Love Languages and Tender Warrior. Those two books have taught me so much about my relationship, learning to speak my wife's language, the deep differences between men and women and so on.
I've been married for almost 3 years, but with her for 8 and we were on the verge of divorce after year one before I buried my head in these books (and stopped associating with friends who gave advice like Deathlok2001.) Now, we have the best relationship we've ever had, because I've put the work in.