NVidia hasn't been putting out the same cards, all of you are wrong about that.
Performance wise, the bar hasn't been moved that much, and yes they have released cards that are similar in performance to older cards. However, they were IMPROVED.
Do you guys forget that the graphics card cycle always goes:
Step 1: Release super-powerful-power-hungry-extremely-hot graphics cards
Step 2: Improve the card to reduce power consumption and heat production while maintaining similar performance
Step 3: Repeat
That is how it always has been, and always will be.
Saying the 8800GTX and 8800GTS 512MB 9800GTX are essentially the same card is idiotic. Performance wise, yes they are similar. However, the 8800GTX is a beast of a card when it comes to power usage and heat production. The 8800GTS and 9800GTX are leaps and bounds ahead of it and the 9800GTX is far better than the 8800GTS.
All the cards the nVidia puts out are either improved in the power and heat areas, or have different performance levels.
I wouldn't say ATi's been so bad with their stuff though. There have always been something similar to a "pro" and an "XT" in both NV's and ATi's cards. Atleast the 3800s brought something new, lower manu process, lower price, lower power consumption and heat output.
Ati's upper end is only 3850 - 3870 and 3870X2
NV's upper end is - 8800GS - 8800GT - 8800GTS - 8800GTX - 8800 Ultra - 9600 GT - 9600 GSO - 9800 GT (soon) - 9800GTX - 9800GX2. bold = using the same core. 9800GTX is pretty pointless, and the 9800GT will most probably be just as pointless. 9800GX2, fast, but overly hot, over priced, slapped together, and, in my opinion, just as pointless. At least the 8800GT/GTS are appropriately priced and are good performers for what you pay.
Though, I think it would be pointless for ATi to bring out a 3830, there shouldn't really be a place for it, the 3850 is pretty cheap as it is.
Wait, you are including nVidia's old card in their upper end, but not ATi's. Why? Because you want to make them look better?
Lets take a look at ATi's real upper end.
ATi's upper end is - HD2900GT - HD2900Pro(256bit) - HD2900Pro(512bit) - HD2900XT -
HD3850 -
HD3870 -
HD3850x2 -
HD3870x2
NV's upper end is - 8800GS - 8800GT -
8800GTS - 8800GTX - 8800 Ultra - 9800 GT(soon) -
9800GTX -
9800GX2
I've also bolded what cards use the EXACT same core, correcting your mistake, the 8800GT uses G92 cores, but shaders are disabled and the 9800GT is using G92b which will have the same specs as G92, but will be 55nm. Though I wouldn't be surprised if they move the other G92 cards to that core also.
Oh, and the 9600GT and 9600GSO are mid-range cards, not upper end, unless you want me to include the HD3650 in with ATi's upper end as that is what the 9600GT is really meant to compete with. So once the two are compared accurately, that leave 8 cards on each side in the upper end. And I could have even broken it down some more and seperated out the HD3870's with GDDR4 from the ones with GDDR3 and added in the very soon to be released HD3870x2 with GDDR4.
Personally, I like nVidia naming each card differently. You can look at the name and tell exactly what the card has, and what its features are. That simply isn't true with ATi's naming and they still managed to have just as many cards types out as nVidia. I don't like the fact that I could buy an HD2900Pro and not know if it I am getting the 256-bit buss or the 512-bit bus, and it drastically affects performance.
Saying the 9800GTX is pointless is exactly the same as saying the HD3870 is pointless. Saying the 9800GX2 is pointless is also exactly the same as saying the HD3870x2 and HD3850x2 are pointless. The 9800GTX is very appropriately priced, it is only $50 more thant he 8800GTX512, and you get your $50 worth. The 9800GX2 is also priced pretty well in the $530 range.