I rarely encounter glitches, but I think that may be because I primarily play Japanese games. The Western game industry seems to be more accepting of glitches since patches are a norm. Plus I'm guessing Japanese games go through two runs of QA (in Japan and then during localization). I also don't tend to attempt to do really wonky things in games.

Pretty much any game will glitch under the right circumstances. It's not so much that a game "has" glitches, as in having a section of bad code, but rather the code won't function as expected when receiving input that wasn't expected. The important difference is how the glitch is encountered. If you have to do something really precise and outlandish, then who cares. If you encounter a glitch just through normal playing, then it's a problem.