It ruins the purpose for me. I play most games as 'challenges' to overcome. I put that in quotations because games are linear checkpoint and ammo spamming hand holders. I have used guides but only when I have tried everything I can think of and nothing has worked. Many times I look up a guide and I get pissed because I tried that and it didn't work. Now that the guide says it, it works... horseshit.
FOr me saying you beat a game means you picked up a controller with no knowledge of what lay before you and you made it to the end. Using Demon's Souls, (I haven't played Dark Souls) anyone that says they beat Demon's Souls, I give 1,000 awesome points to in my brain. If they admit to using a guide or that someone who had already beaten it played backseat driver, it drops to 200 awesome points. A lot of Demon's Soul's challenge is not knowing wtf is going on.
For what its worth, beating a hand holdy game like Uncharted, RDR, Fallout, etc. is only worth like 100 'awesome points' to me as far as accomplishments go. Then anywhere between 0-10 points if you used a guide.
The problem I personally have with using guides is that everyone I have ever known to use guides likes to inform me that I am not playing 'optimally' when I talk about the game.
Guide User: DId you get the Rocket Launcher of Fiery Explosion?
Me: I didn't even know their was one.
Guide User: Yep, *describes how to get it*. It dominates everything.
Me: I seem to be dominating enough with conventional weapons and checkpoints.
Guide User: Have you got all the hidden items?
Me: Nah, I don't think so. I don't really hunt those down.
Guide User: I got em all. I have the game 100% completed.
By this time I no longer want to even talk about the game with them. However, let's assume a week later I finish a challenging part of the game. I am excited about how intense things got and want to tell the story of how my playthrough went.
Me: Oh man, I just got past the cemetery section. That was insane I didn't even realize that I was supposed to get to the mausoleum so I ran around fighting those damned zombies for like 20 mins. It wasn't until I was out of ammo that I realized and they kept grabbing me. Each time I was having to mash triangle and then I would get them off of me only to be grabbed again. By the end my thumb was sore.
Guide user: You should have gotten the rocket launcher of fiery explosion, I just strolled to the mausoleum blasting them along the way.
Me: Shut up. (Obviously unaware of the entire REASON I wanted to tell the story)
My brother recently tried playing the Last of Us and in the first room full of clickers (Subway) where you are supposed to sneak by them, he ran in and spooked the first one, ran from it and spooked the rest of them. However, he made it to the center of the room and hopped the wall. He explained he was hopping the waist high walls trying to figure out where to go and distance himself from them. I thought this was a story about his first death by clickers as he went on. Then he explained that he came to a dead end and turned to see an army of clickers charging at him and he pulled out a molotov and threw it since they were all clustered before hopping a waist high wall and taking off running. He killed every clicker in the room with 1 molotov cocktail. Now, that is a damn good story. That's hard to pull off even if you know what you are trying to do. Just for doing that he scored like 500 awesome points in my book. That's the kind of cool crap that guides will rob you of.
I can understand someone using a guide to see content in a game but not having time to see what they want to see. I totally get time constraints. I get being OCD and having to get all the collectibles. But using a guide does discredit the "accomplishment" in my eyes. To each their own and if you like playing that way, have at it. My perspective isn't their to tell people what they can and can't or should and shouldn't do. However, I do prefer to talk to people about games that don't use guides, more specifically rely on them. (Guides rob you of the in-game struggles - having to go through the motions isn't a struggle) The people who buy a guide for a game at the same time they purchase it are a completely different kind of gamer than me and they can tend to kill my fun every bit as my perspective can tend to kill theirs.