Right.
The
GF4 cards image quality is much better than the GF2 & GF3 cards and EASILY on par with ATI cards.
The
GF4TI4200 is a fair bit faster & excellent o/c, more so than any current Radeon and also has much better AA (enhances image quality for games by removing jagged edges).
The GF3TI200 WAS good value for money, but the Radeon8500LE is faster, cheaper and has better image quality (in the US & Canada, outside Radeons are a rip-off).
BEWARE! Non-ATI Radeons (eg Hercules etc) use cheaper RAM and seriously underclock the Radeon cards, unless a total bargain get an ATI Radeon!
I would say it comes down to price. The Radeon8500LE & 8500 are very good cards. Excellent image quality, very capable gaming cards and well priced (in US/Canada). The GF4TI4200 also has excellent image quality, is a fair bit faster and a great o/c, but will knock you more cash than the Radeons.
If an extra 10-20% in gaming perf is not the most important thing to you, then get an ATI Radeon8500LE.

I think this is a lot more informative than just giving biased opinion as many people seem to be doing.