In terms of the language I will stick to the polish, because I know it just going to sound the best in this setting and it's going to have the best lines. Some people are complaining about theatricality of the polish version, but it never bothered me and I think that in the most cases it sounded cooler or funnier this way. There are some missteps, like Saskia, but I am willing to forgive it in comparison to the english dub. I'm not gonna sugarcoat it, in the first game english version just sucked. Most voice actors just read their lines without any shade of emotion (like they didn't know any context), translation was terrible and even after they fixed it, many dialogues were much shorter and worse then in the polish version. The english version of the second game was quite of improvement, but still it often sounded really bland to me. The biggest issue in the translation of the second game was that the dialogues didn't flow as good as the one in the polish. By that I mean while in the polish dub they fluently come from one line to another, in the english sometimes it sounds like the character just started talking out of nowhere about something completely different (drinking with the Blue Stripes, for example).
In the third game, judging by the samples, they seem to avoid all of the above problems, but I can't be sure without the proper comparison. Well, I'm going to watch Chris Odd's Let's Play anyway, so I will have a chance to do so. Doug Cockle still does not convince me as a Geralt, but that's just maybe because I just got used to Rozenek, so anyone who sounds any different from him just doesn't feel right. However, I may check out the Japanese version as well, as from what I've heard, the Japanese Geralt sounds like a really good mix of Rozenek and Cockle Geralts.