I've had all 3 and if I were on a tight budget, I think I'd lean toward the N95. The N95 is pretty old and you should be able to find it for a lot less than the N97. Nokiausa.com has it for $369 (they list a few colors and versions at various prices but that's the cheapest). Though it's old it's still a really excellent phone.
The 5800 is a fun phone but the touch experience may take some getting used to since there's no d-pad to navigate around the phone the old-fashioned way you might be accustomed to. obviously the camera isn't as good as the N95 and N97. But the higher resolution display is nice when web browsing (not sure how important that it to you).