FX5200 better than gforce 4?

Short version: Is FX5200 better than gforce 4?

Longer version:
The game I'm looking forward to playing when released (Thief 3)
requires at least gforce 3, NOT MX, DirectX 9, with vertex pixel
shading. In my case it must also work under Win98 1st edition. I
got a card off the net which didn't state the platform and which
I eventually found would only work in Win98 SE and later so I
gave that someone else and went to a local shop instead.

I asked for geforce 4 in the shop and was so pre-occupied with
making sure it worked in Win98 1E that I didn't notice until I
got home it was not geforce 4 but FX5200. I asked on the net and
was told this was inferior even to geforce3. Back to the shop
where the manager insisted that was nonsense and the FX5200 was
better than gforce 4. He was so certain he literally signed my
receipt, "better than geforce 4 - (next level up)"

Questions:

1. Is he right?
2. Is there anywhere on the net I can get an overview of the
evolution of graphics cards in general, the jargon, etc. so I
have some idea what all these letters, numbers, and so on mean?