Is my graphics card causing low fps?

My PC specs are 8 gb of ram, a 3.33 ghz intel core 2 duo processor and last but not least an ati 2400 hd graphics card. I only get like 35-40 fps on runescape on max settings, on league i only get 20-30 and on minecraft I get 30-40. If I upgrade my old *** graphics card to a much more modern one, will I get a huge boost in FPS? Best answer 5 pts, thanks.

Its the graphics card. If you fancy yourself some real power i suggest a Nvidia card like this: https://www.google.com/...MoFEKYrMAc
** if your computer can handle an upgrade