Obviously Ultimate would be the best, but it'll cost you. I'm using Professional and it does more than what I'll ever need!
Ultimate isn't an operating system designation, it's a package designation. Windows 7 is Windows 7. Using Home Premium (if you're not on a domain) is the same as using ultimate.
Of course windows 7 (ultimate) is the best operating system in windows OS's. After windows XP, windows 7 made a remarkable change in the operating system wise.
There is no "best" version of Windows 7. It all depends on what your needs are. Average Home User = Home Premium Business = Professional Multimedia & Business = Ultimate
I have professional and ultimate (professional on laptop) and tbh i havent noticed any difference between the two. They really look like the same OS. I am sure that ultimate has some added features but i havent noticed any.