Argh, I think you're greatly underestimating the graphical power of the new N-Gage platform. 3D chips aren't all-important, software rendering can be just as good as hardware rendering if the device's main processor is fast enough.
NONE of the current N-Gage games use 3D chips. The only reason some N-Gage 3D games look much better than others is that the better-looking ones are better programmed, with better rendering engines.
It's also unwise to judge any gaming platform based on its first few games, because developers take time to get used to it. You have to wait at least a year or more to see any system at its best, and that has always been the case since the very first gaming platforms of the 1970s and 1980s.
and I'm pretty certain that 99% of games on any Sony gaming phone will also be 3D. Down-converting most textures to lower resolutions isn usually cheap and not too much of a problem, but remodelling lower-poly versions can be far more time consuming and expensive.
You're assuming the Sony Ericsson phone would definitely use 3D chips, but that's not necessarily the case. If they do an N-Gage-style platform across a range of models then they might avoid chips so that they can spread the platform as widely as possible and reach as wide a userbase as possible.
Sony already have the PSP, they don't need to make another dedicated gaming device. The point of a phone gaming platform is to reach a wider audience than consoles can, and a 3D chip would restrict how many phone models could work with the platform.
On the other hand, maybe 3D chips will become commonplace in phones, but that would probably happen simultaneously in both Sony Ericsson and Nokia phones, so it wouldn't be an issue when it comes to porting games.
Down-converting most textures to lower resolutions isn usually cheap and not too much of a problem, but remodelling lower-poly versions can be far more time consuming and expensive.
You definitely don't need 3D chips to do DS-quality 3D graphics.
The new N-Gage platform doesn't currently use 3D accelerator chips, but the phones on the new platform have 300mhz - 350mhz processors while the DS has just 70mhz. (I think modern N-Gage phones also have a lot more RAM than the DS?)
N-Gage phones' much greater raw computing power means they can render good quality 3D through software alone, which might not match the PSP but it certainly matches the DS and even goes a bit beyond it.
System Rush Evolution looks so good because its developers Ideaworks3D have an extremely good graphics engine and they've used it very effectively. They've always been the best developer on N-Gage, even on the original gen they made it perform miracles. It should be very interesting to see how Ideaworks3D handle the upcoming Metal Gear Solid game which they're porting to N-Gage, as that could be quite a graphically-intense title.
Having said all this, Nokia has stated they will use the 3D chip in the future, but apparently they're waiting for it to become more widespread. At the moment only the N95, N82, N93 and E90 have a 3D chip, and the E90 isn't even part of the N-Gage platform.