What is the difference between two versions of the game? Are there any gameplay changed, or the graphics update is the only thing?
Spelunky HD includes quite a few new features and additional, reworked content, including;
- updated graphics
- new enemies
- new areas
- new terrain
- new items
- new playable characters
Here is an image demonstrating the differences in updated graphics;
Additionally, since Spelunky HD has been released for multiple platforms, you get some platform specific content. For example, for Steam on PC you get trading cards and achievements via Steamworks. The GOG release is DRM free. The PSN release includes cross play and purchasing it via PSN allows you to play the game on both Vita and PS3.