I'm going to go with The Witcher. It'll probably still be selling OK amounts when the next generation of consoles start up and Mass Effect sales will drop on 360 as focus shifts to the new consoles. Of course by that point it'll be dead cheap and probably have a Witcher 1&2 bundle.

Would be interesting to see the legs of Mass Effect on the PC and see how that compares to both Witcher and the 360 version.

Do you actually have proof of these sales? Or is this more of your rampant speculation based on Steam rank like you did with CoD4? Next thing you will be hearing is The Witcher sells 5 million on PC!!!!

EDIT:  I see you mentioned the Devs released these figures or some nonsense.  I found the video where they gave the total, but I think your other figures are just your own made up guestimations.

600k: http://gamernode.com/news/5948-the-witcher-sells-600k-copies-surprise-on-monday/index.html

1 million: http://www.shacknews.com/onearticle.x/55654

1.2 milion: http://www.shacknews.com/onearticle.x/57541

1.5 million: http://www.thewitcher.com/press_release.php?l=en

Thank you   Now I advise you to add that kind of information to the OP in the future.

Wait, you get me confused.
Why compare the sales for The Witcher to the sales for ME2... on Xbox 360 only?

if it's against the 360 version only, then it's very possible.
Also ME2 came out simultaneously on 360 and PC... which was not the case for 1 if I recall.... sales so far are dropping much faster.

Sales
0.03m
Japan

1.48m
Americas

0.66m
Others

2.17m
Total
1 17,469 258,341 118,947 394,757
2 3,755 199,026 68,499 271,280
3 1,954 104,080 38,325 144,359
4 1,097 97,160 38,674 136,931
5 833 117,758 45,638 164,229
6 666 57,957 33,672 92,295
7 570 36,566 18,800 55,936
8 437 27,073 10,341 37,851
9 388 21,787 13,537 35,712
10 335 24,026 11,186 35,547

against


Sales
0.00m
Japan

1.18m
Americas

0.43m
Others

1.61m
Total
1 n/a 726,800 234,490 961,290
2 n/a 178,737 89,340 268,077
3 n/a 109,638 42,210 151,848
4 n/a 61,625 22,266 83,891
5 n/a 36,784 18,372 55,156
6 n/a 28,574 9,291 37,865
7 n/a 20,047 6,494 26,541
8 n/a 14,487 6,140 20,627

It is clear that ME 2 in it's current form will not greatly over shadow ME1 on 360

Also, the witcher 2 is expected to beat it's father in sales... afterall now the dev has a record.

i'll vote yes just because it's possible... though when all is said and done the witcher is not sure to pass 2M.

Mass Effect 3 is all but announced.  I'm pretty sure it's widely accepted amongst everybody that there will be a Mass Effect 3 likely in 2011 and anyone who doesn't think there will be one is simply a moron.

Witcher 3 on the other hand is absolutely up in the air.

You think 2011 is more likely than 2012?

Witcher probably it still sell for 60 PLN in Poland and has two or three more bargain series to go through before almost mandatory release in one of gaming newspapers as cover cd, and after that it will be getting releases as a bundle with Witcher 2.

I think Witcher selling for 9.99 on Impulse at the moment. PC games tend to sell for nicks after all has been said and done. To get a console game at this price is a lot more rare. So, since The Witcher is so cheap, it's unit sales will get boosted a lot more. But revenue compared to ME? No way, I think.