Question really is how much did it cost, and would 2 lesser cards be available at the same cost, and are they faster. IE if you spent £400ish, would 2x460gtx's(i really don't know how they are in sli compared to a 480) or 2x5850's be faster.
The answer is probably that the 480gtx gets pretty well spanked in both situations, for potentially lower cost(not sure how much an EVGA one goes for as ocuk don't have one).
I've said since launch, its faster, but meh, its still not worth the cost, theres better options, the ONLY time i'd consider a 480gtx is buying 3+ of them, because at that money/performance nothing can touch it. IF money is no object then you can't beat multiple 480gtx's, but at any specific price point, theres better options, maybe much much better options.
It also seems like somethings a tad up with your numbers, as the difference wasn't really seen in a single review to date, from launch, or from 460gtx reviews which redid 480gtx results with latest drivers.
Also intentional or not, its basically all of Nvidia's strongest games in together, even so the numbers don't quite add up, could it even be you overclocked the 5870 too far, where you can lose significant performance rather than gain it, but not crash out or become unstable.
Meh, anyway you cut it, realistically if the 480gtx cost more than about £370, for the same money you can get significantly more performance, and if it cost a bit less then 2x 460's/5850's would cost you more, but performance increase would be greater than the % cost increase so still much better value.
My other fundamental view, which I've said in most threads, is business wise, the 480gtx again was never a bad card, but a company that can't make money on a £400+ gpu, is failing, and if it does that for generation after generation that company will stop existing because thats how life works. THe cards need to make profit to cover manufacturing costs and staff, and needs to make further profit to cover what add's up to billions over a few years of R&D costs.
GF100/GF104 and most likely 106/108 are utter failures economically, which long term means no Nvidia, which long term is bad for us all. 480gtx, highest possible performance with multiple cards, check, good value for money at really any level, nope.