U just have to remember that there are also benchmarks in the internet where 7800GTX beats the x1800 XT in games like splinter cell: pandora tomorrow etc. Also I have seen benchmarks where the 7800GTX pwns in HL2. (can't remember the links, someone posted them here awhile ago) But all of them are not too reliable.
But they seem to be quite equal cards. Ppl say that the x1800 XT oc's very well, but I haven't seen any results so it's hard to say. And it seems quite clear that the x1800 XT is better in 3dMarks, yet still the top 10 in futuremarks page is done with nvidia, not a single computer with an ati card(s) in there.