QWOP!! Boy that was an old memory. Haven't heard anyone mention that game in over 7 years. Back to the question at hand...
When it comes to racing games like Need For Speed Most Wanted 2005, I don't mind using the keyboard. Mainly because the response times seem pretty fast and accurate. I will say playing games like Fifa and Tony Hawks Pro Skater are nearly impossible on the keyboard. For games like this, a USB controller is required.
On the opposite end of the scale, playing first person shooters like Counter-Strike: Global Offensive is IMPOSSIBLE with a controller. Majority CS:GO players use their keyboard and mouse. So instantly when you plug in a USB controller, you can feel the delay time and inaccuracy really takes hold.
On a side note, I never liked the joystick growing up. My mother bought me one when I was a child, I never quite figured out how to use it. The games I wanted to use the joystick, weren't compatible (and vice versa). Within a few weeks of buying one, I sold it off to a friend.
So my opinion is, when it comes to PC games (keyboard vs controller), it depends on that particular game you are looking to play. I suggest having both available to cover your gaming needs.