So I was skimming through the Half Life wiki and on Wheatley's Page down in the behind the scenes section it says that Richard Ayoade was the original choice for Wheatley's voice.

I love Richard Ayoade in everything he does but a lot of that comes from his physical performances as well as his voice so I don't know how well he would have done as Wheatley and after experiencing Stephen Merchant in that role its hard to imagine somebody else.

For those not aware of Ayoade's work, this pretty much sums it up:
  

dont even joke about Matt Berry being Wheatley... i'm pretty sure the world would of imploded.

I think Stephen in the end was a better choice voice wise. Richard though... love him

They should have opted for him.

Merchant did a great job, but his brand of comedy is so consistent throughout everything he does (and near identical to his partner Gervais) that I became tired of it a long time ago.

Matt Berry has the best voice ever

turned out for the best, i guess. merchant was terrific.

You and he were, buddies, weren't you?

Saying "first choice" makes it sound as if Valve wanted Ayoade, couldn't get him, and then went with Merchant. From what I've read this isn't the case.

From the interview that the wiki you linked to cites as a source:

Was he the first person you thought about for the role?

Erik: We had him in our heads when we were writing, because we’d been watching Extras and we really liked him. We wrote the character with him in mind not ever thinking we’d be able to cast him. In fact we’d been in contact with Graham Linehan, the writer of The IT Crowd, because we were thinking of getting Richard Ayoade in, but he’s got a very different vocal style than Stephen Merchant. We thought we’d go to Stephen Merchant’s agents first and see if he’s interested, and he said yes. It was kind of a side-step into our dream casting.

We’re big British comedy fans, we knew we wanted a proper British comedic voice for this character. Who that would be however was sort of up in the air until we actually cast Stephen.

Merchant is awesome as Wheatley, I'm glad they ended up with him

GIANT BOMB IS ALIIIIIIIIIIIIIIIIIIIIIIIIVE!!!!

Stephen Merchant as Wheatley is uber-annoying. There's a certain smugness, a certain self awareness of the role he's playing which is irritating. Dean Lerner would have been my main go to man, when you want a professional job done, whether voice acting, or running a world class hospital unit in Wolverhampton, Lerner's your man.

Wheatley was fine, internet.

I think they made the right choice.

I love Merchant Wheatley, but dang do I love Richard Ayaode. They couldn't have gone wrong either way.

" Wheatley was fine, internet.

Also the IT Crowd is fucking dumb. Its English Big Bang Theory.

"

I'm sure Ayoade would have been great but now I can't imagine anybody else as Wheatley, the placeholder voicework for him just seems really weird to me now.

and The IT Crowd has some great moments, I definitely prefer it to The Big Bang Theory. Although it has gotten a bit worse since the last series but still pretty good comedy.

  

" @ryanwho said:

" Wheatley was fine, internet.

Also the IT Crowd is fucking dumb. Its English Big Bang Theory.

"

I was about to nerdrage on this, but I'll just put it down in three points:- IT Crowd was created first by almost a year- Written by Graham Linehan, one of the people behind Father Ted and Black Books- British Humor, may not appeal "

I like Richard Ayoade, but i'm glad they went with Smerch. He was absolutely brilliant.

" @Tregard said:

" @ryanwho said:

" Wheatley was fine, internet.
Also the IT Crowd is fucking dumb. Its English Big Bang Theory.
"

I was about to nerdrage on this, but I'll just put it down in three points:- IT Crowd was created first by almost a year- Written by Graham Linehan, one of the people behind Father Ted and Black Books- British Humor, may not appeal "

You can chalk it up to the humor being too subtle and tongue in cheek if you want. I don't get Benny Hill either. "

Richard Ayoade would have been awesome. But the guy they picked wasn't too shabby either.

The role was written for Merchant but Valve thought they wouldn't get him and started to think of alternatives but then Merchant said yes. That story was posted here in the first page.  Merchant was brilliant in that role which was well written, the character was one of the best things in the game. I do not think Ayoade would have been as good, and besides isn't he a director now.