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: 
'Perfectly': never. 'Very Good': usually. Professionals tend to want to show you what they can do, rather than what they can't; it's their meal ticket, after all.

One of the skills in being an instrumentalist though is to practice techniques that allow you *to* power through small mistakes without disrupting the rhythm or the overall feel of the song, or letting your small mistake trip you up and turn into a bigger one. Pros will generally be good at this aspect of instrumentalism too; it's one reason you may not notice their mistakes.
I am not a guitarist myself, but I know a really great one and he assures me that he has never played all the way through a song without making a mistake, nor has he ever played a piece through exactly the same way twice. He's always tweaking things here and there. If you're comparing yourself to recordings, you have to realize they do multiple takes and combine the best takes. Even then, nobody is hardly ever perfect.

And please do silence your conscience! This is not what it's there for!