I would also have to go with retro. There are many retro games in my backlog, so having an excuse to forget the current stuff would be nice.
Retro all the way. I tend to dislike most new games especially ones from big name publishers, though I do have a love hate relationship with Paradox.
That depends on what you consider retro. Personally I consider it to be anything 10 years or older. For that reason I have to go with modern. I love retro games, but my collection is just too small. The majority of my games are from the last ten years, so I'd have more to play with.
I red your post and then thought about the question and then realized that the OP's question does kind of consider on what is considered retro and the difference between retro and retro style games. Take for instance the different Spider Software games. Yes the bulk of them are retro games (and despite the graphics of some they are still fun) However they recently did a remake of the first Genoforge game and they did update the graphics and made some QL changes it still in the same stile of the Avernum remakes and makes for a smoother game play. Anyway just thought I would put this out there after reading Neb's post.
A week is nowhere near enough time to finish the kind of retro games I'd be playing if I was stuck with those for a week, haha. Honestly though, it depends on what we're classifying as "retro" here. If it's according to my sensibilities - anything before the sixth generation - then I can't say I'd particularly enjoy being stuck playing games from that era for a week. Whilst a lot of the most influential games of all time came from the fifth generation and before, "influential" does not necessarily mean "best" and, frankly, I find going back to a lot of old titles almost physically painful due to the QoL features implemented in modern games that make them a much smoother experience, even if they're not necessarily as fresh. I mean, much as I love Final Fantasy VIII, I wouldn't want to play the original PS1 version instead of the Remastered version on my Switch, as one example. But I realise that "retro" is an ever-expanding concept, and we're in the tenth generation of consoles now. The seventh generation started in 2005, so there's definitely an argument to be put forward that the Xbox 360/PS3/Wii could be classed as retro systems now, especially since games are no longer being made for them. I wouldn't mind being stuck with PS3 games for a week...although I might need longer than a week to replay Tales of Xillia and Tales of Xillia 2. Although again...QoL improvements. The eighth generation was very much a remaster generation, and I'd definitely sooner play PS4 remasters of PS3 games on my PS5 than I would the originals, and Xenoblade Definitive Edition over the original or 3DS port. ...in fact, since modern platforms have a massive retro library, and I can make up the difference with emulation if I really want to, I'll just stick with newer hardware. It runs faster, the controllers are more comfortable, and the library is just bigger and more inclusive.
I'd have to go with modern. A week isn't really that long and I'd make do with either regardless of where you wanted to draw the line between retro and modern, since there's not really anything clear with that, but I play Smash Ultimate too often to justify getting rid of anything else. It's the only thing I play several times a week, and there's plenty of other modern stuff I enjoy to go with it.