So I'm going to break with convention here and throw this one out and see what you all think.
So usually a guy who is 6ft and above is seen as admirable. However, I going to equate that about like a girl with big boobs, say D cup and above. Many guys get off on the girl having big boobs but in reality while they would go with them (looks, etc aside for the moment) they really see girls with B & C cup boobs as the most realistic, practically speaking.
So I'm going to say with guys, although girls admire tall guys, realistically speaking they find a guy with say about 4-5 inches higher as being more practical and hence a more better match. Since most women are about in average around 5'4" to 5'6" for those women that would put guys around 5'9" to 5'11" as the practical ideal and hence in reality more acceptable to most women.
A lot of this I'm going to put down to how the two sex's line up sexually. In the most common 'missionary position' a guy who is around 4-5 inches taller than the girl will line up pretty much face to face once the penis is inserted, since he will be going about 4-5 inches lower than the woman to do this. Lining up with each others face of course is ideal as it means you can kiss easily while having sex. That of course is going to be way, way better than a 5'4"-5'6" girl with her head resting on your chest or even neck. Kissing while having sex without interruption is near impossible with that kind of line up and that's a real bummer.
There are of course the odd different positions that may be taken up and they can be good but if course the missionary position is most popular for the reason that with the correct line up of heights it offers the most in return.
Therefore, I'm going to state that women in reality tend to more readily go for a roughly 4-5 inch height difference (with the man being 4-5 inches taller) as the most acceptable ideal to them. While the 6ft plus guys are more a kind off height porn to them. Sure they could get with them and may do, but it's not really the ideal (not unless they are at least 5'8" and above) so in reality they see the 5'9"-5'11" guys as the ideal depending on what they are height wise around that.
I'm not saying you won't see short girls with tall (6ft plus) guys in all of this, you obviously do but that the common conception that women mostly want 6ft plus guys is fundamentally incorrect, that many will more happily go with the 5"9-5"11" guys.