Well you are about to hear alot of things from alot of people. According to all the research I did including the paper I ended up writing for school, and even the information on my website - the differences between the versions are differences in features, not differences in how good the core OS is.
I chose to get Ultimate because I wanted to familiarize myself with all the topics vista has to offer because I am basically responsible to know hwo to fix them if they break heh (not that I have used thenm all yet).
Basically - you really want to stay away from Basic. Vista basic is a downgrade from XP home - it has almost nothing (it even has less windows games like chess and stuff).
Once you get to Home Premium you have Aero and just about most everything else including media center edition stuff. Everything that related to entertainment is present i this version.
Business is the version that takes out the entertainment stuff and adds productivity tools.
Enterprise is similar to business and ultimate but if for large companies that buy licences one eyar at a time and 1000 coppies etc.
Ultimate - there is not any feature missing from ultimate and infact, windows updates has optional updates with small tidbit programs that are only availible to ultimate users (or first availible).
For more details clikc here:
http://www.microsoft.com/windows/products/windowsvista/editions/choose.mspx
Also, if you are getting it for gamming - you might as well get the 64bit version since one day, games will take advantage of it. (or if you want more than 4 GB of memory someday)