Question: I playing guitar since a couple of years (but not regularly) and I always wondered if guitarist from known bands always play their songs/solos perfectly?
Especially when the songs are fast paced, is it easier to make mistakes that no one will notice? When I play solos I am never really satisfied with my performance since it doesn't sound exactly the same like in the song.

I know there is no exact answer but I would like to know what you think so I can silence my conscience :)

Answer: 
If you are talking about mistakes made during a live performance, all guitarists make them and most of the time they will not play solos note for note as recorded on the studio version (see the many Youtube videos of Steve Vai's original and several live versions of "Tender Surrender").

If you are talking about a recorded performance, as @Todd Wilcox noted, mistakes are hardly ever left on with most music genres as they are so easy to fix.

Of course in jazz, blues, etc., guitarists make mistakes on solos all of the time but you probably won't notice them as they will just turn them into a new ideas as solos are for the most part improvised (live and studio versions). Mike Stern told me many of his best ideas came from errors and variations on them.
Other answers are great, but I'll add my experience. When playing live with a band, you have a lot going on at the same time. So mistakes may be masked by the rest of the band.

Most importantly though, is that you roll with it. Not just from the perspective that mistakes can still work, but that if you let it get to you, you are more likely to make more mistakes. Instead, just keep going, the audience can't rewind to hear your mistake again. If you can finish strong, that's what they will remember.

I love this [video](https://www.youtube.com/watch?v=wn1pk8Lpelc), and it's the perfect example of rolling with it. SRV breaks a string and his tech replaces the guitar in basically a four measure break that was there anyway.