All those people who call 4850 "the clear winner" need to look at actual benchmarks instead of generalizing. Overall, 4850 would still qualify as the winner, but not by nearly as much as the hype would suggest, and there's nothing "clear" about it.
It all depends on resolution. 4850 consistently outperform 9800gtx/g92 8800gts at larger resolutions, but the opposite is true for 1280x1024 or below. Although low by today's standards, many people still use 1280x1024 resolution, or the widescreen counterpart of approximately the same area.
See benchmarks, performance very in different games, but there is a general trend as resolution increase.
Of course, there's also the issue of overclocking. Those benchmarks are done on stock cards. For example, pro reviewers have only been able to oc 4870 a mere 7%, while the 8800gts goes from stock 650mhz to 780mhz (20%) easily enough for typical home users to manage using free utilities like Rivatuner.