There are many types of PC controllers which is kinda good for us gamers as we can use the best pad that suits us. The worst aspect is the way M$ try to force PC gamers into using 360 control pads and the way many games dont allow your to re-configure the buttons. Luckly PC gamers can use 360 pad emulators and Xpadder to bypass / fix all that
As for what pad you want to use, its really up to what games you play. If you play 3D games then many analog pads are fine. The problem arises when you want to play 2D games and make use of the d-pad as so many modern analog pads have shockinly bad and unusable d-pads (eg ps2 clones from logitech or saitek) . It's like everyone has forgotton about the d-pad as everyone has gotten used to using their analog sticks to play 2D games like super meat boy or retro games.
However as any 2D game fan who has a decent d-pad (or an arcade stick) will tell you, 2D games arnt ment to be played with an analog stick its like using an decoration paint brush for fine art. (just try playing contra or a bullet hell shmup). Unfortunatly so many modern gamers are so used to their analog sticks that they'll stick with it and it doesnt help when so many modern pads have substandard d-pads.
Ild recommend gamers buy an analog stick for 3D games and also buy another pad thats designed for 2D games like that SFiV pad ^^ or the modern 2D figher pads or my personal choice an sega saturn reproduction pad as the saturn / MD d-pad is widly accepted as the best there ever was.
The current pad im using is a GameWare PC pad. Its a ps2 clone with a decent d-pad plus built in auto fire. I did have an Sega Saturn USB pad I bought off ebay shipped from China and would replace it if the price hadnt jumped from £12 right up to £50 now these are becomming rare and everybody knows they are so bloody good.
I might get those new US saturn repro pads for around £15 but I hear the build quality is shite compared to the Chinese version (crazy isnt it)
I might get one of those Marvel Vs fighting pad instead as it has mechanical switches instead of those cheap and nasty rubber ones with the thin coating of metal that wear away quickly if you button mash http://www.youtube.com/watch?v=eyxVRTCVjVo
Heres a picture of my Gameware pc pad with the decent d-pad http://www.gametechreview.com/compare/pc/hardware/332015/gameware-pc-rf-control-pad.html
I have the wired version though. I prefer wired pads as wireless adds lag which is a bad thing for fast arcade games