No offense to your girlfirend, but that kind of stuff is really annoying. It can be worked on but I do not believe men should be coerced into always agreeing with their women on the "cuteness" factor, esspecially when it means squelching their own opinion, solely due to insecurities. No matter what, there will always be someone else out there who is
*gasp* cute, hot, or beautiful, maybe even more so than the women (or man). My boyfiend has a sister who pulls this crap all the time but to the point of making a huge deal out of it, tearing her boyfriends head off (literally), and basically ruining the good times of everyone around her because she can't deal with the fact that she isn't the only girl around. Her BF (and there have been MANY due to this) can not even be in the same room with a pretty girl without a giant fight. It's gotten so bad no one wants to hang out with her. I try not to get upset and understand that it's coming from her low self-esteem but it is very difficult when I get told by her that the only reason I can appreciate a woman's beauty is to get brownie points with her brother (OMG how wrong can she be!). No, it's because women are beautiful, every single variety of them, and that should be admired, not despised just because they may be more beautiful than me.
Wow, that was a bit long.
You may have hit a nerve!
I will close by saying your (the OP) girl must be one hell of a woman for you to be ok with that. Reinforce the fact that you love her and not the girl on TV you think is cute, and let her know that you are entitled to your own opinion. I hate to say this, but by appeasing her when she does this you may be setting yourself up for (for lack of a better word) a wee bit of brainwashing.