Well, that's why there's a vote counter, right? Not that I think GOG should, or will, ignore the less popular ones, of course. Just that the highly rated games will probably get higher priority.

No it isn't. Programmatically handling duplicates would actually require tacking on orders of complexity that I think is totally unnecessary.
For example, how do you handle the fact that games are published under different names in different countries? Or the fact that people may often misspell games? pkt-zer0 above made a suggestion for how to handle this which I think is absolutely ridiculous in that it just lumps on this crazy complexity.
Right now the UI of the Wishlist is designed such that a person will search first because it's the default option. Will people still occasionally create duplicates? Yes. Will those duplicates be ignored by most people? Yes. Does the system function to give both users and Gog exactly what they want irrespective of some duplicates popping up every now and then? Yes.
So use it, and stop trying to make this Wishlist some hideous feature-bloated monstrosity.

A Note for the guys who run the voting thing, you have crusader no remorse and crusader no regret in the polling twice! once with a ":" and once without, you might want to consolidate those!

The same person who put "Crysis" and "Mass Effect" on the list. /facepalm
I think the "Add Game" link should send an email to somebody at GoG who moderates the list - dumping requests such as these three games, and dumping the dupes.

Why not just let the community self-moderate?
Obviously, the majority of us realize Crysis is a stupid suggestion and will never vote for it, so who cares if it even exists in the list?
I'd rather have ever person at Gog devoted to doing something worthwhile (new content, community interaction, etc) rather than filtering idiots. And I'm sure they would too.

I'm going to wait and see, but my guess, judging by how many Black and White titles there are, is that dupes are going to keep coming in and people are going to keep randomly voting on one or the other not thinking about dupes.

I agree that there are many hidden gems that won't stick out on the wishlist as it is, but I believe that GOG is probably first going for commercial viability and making the most people happy before promoting "underdog" titles. The more titles they sell, the more likely this site will be around long-term.

Lovely feature. And I'm impressed at the community for suggesting all the good games. :D
(Seriously, even Battle Bugs is on there. What more can one ask?)
That depends on how it is solved. A simple solution would be a little button for "mark as duplicate". You then get a little textbox where you can enter the url of the game it duplicates.
GOG staff/moderators/whatever can then read these submissions and (the easy solution) delete one of the duplicates and transfer the votes to the remaining one, or (slightly more advanced, but still pretty straightforward) let one be an alias for the other. So when you vote for X-Com: UFO Defense, it automatically adds the vote to UFO: Enemy Unknown, because they're the same game.
Of course automatically detecting duplicates would be a pain to do properly (but should still be done in the simple cases. People suggesting Fallout should get a little notice pointing out that it's already available, for example)
In fact, the 'add game' button should automatically perform a search and if a perfect match was found, use that instead. If similar names are found list them so you can see what similar games have been suggested already. Remember it doesn't have to be 100% guaranteed to eliminate duplicates. If it just makes it more obvious when you're submitting a duplicate, that's good enough. And if there's some mechanism to request a merge of duplicates after they've been created, we've pretty much got a win. None of this is rocket science to code.

Perhaps GOG should add functionality to check for similar results. Then ask the user "Did you mean this game? [insert game here]" before allowing them to add a new game.
Similar to the way google works if you spell something slightly incorrectly.
Not sure how difficult that would be to implement though.

I've been voting for every game, because I believe every gamer has a right to play their favorite game without DRM or other hassles. Now, I know some of those simply won't be possible. Selling Bioshock at a 9.99 price point, with no drm, soundtrack included, and artwork? yeah, nope, not for at least another 3-5 years.
But, if enough people vote for an item, it's quite possible that GoG will speak with that publisher, and perhaps they'd be able to work something out.

Hmmm...doesn't seem to be the case anymore.
A search for "Black and White" turned up 0.
"Black & White" has 79 votes.
Looks like the Gog guys are doing some dup. fixing behind the scenes.

Not really, it's just one level of indirection. You search for names, and names are assigned to games, which have a single primary name. If you denormalize the tables, there's no need for a join, either.
I don't know for sure whether implementing this or having to manually deal with duplicates take more effort (depends on how many duplicates there are), but I thought the idea was worth tossing out there.
Having users add name variations would add possibly unneeded complexity to the user interface, and could be misused just as much as the main list, thus requiring more moderation by the GOG team, the opposite of the desired effect. Hence the "possibly" in my suggestion.

Thanks, I'm glad to hear it's being worked on, and I am also glad to see you didn't include "merrily" in quotations.. hahaha.