Not sure if ASUS ROG line is necessarily needed if you intend to play mostly old games, but they are good for PC gaming, and are in various price levels nowadays. So a cheap ASUS G-series laptop might be ok, if you agree with the price. At least here the prices for G-series seem to start from 999€, though (and up).
E.g. this one:
http://www.kannettavatietokone.fi/Kannettavat/Asus/G551JM-CN061H.html That should play also semi-new games quite comfortably, and newer games too with somewhat lowered details. Maybe Witcher 3 will be too much for it, though. :) Maybe that laptop is generally about the same speed as my older G75VW gaming laptop (not quite sure which has a faster CPU though).
Since you wanted SSD, the price doesn't include a SSD drive though (but a 1 terabyte 2.5" HDD), not sure how much the price would go up to replace it with a SSD. EDIT: Well, it says a SSD replacement would cost an extra 200-300€, depending if you want a 250GB or 500GB SSD. I'd personally keep the 1 terabyte HDD, but that's just me I guess.
Overall I am generally happy with ASUS products. I have bought one laptop (G75VW) and two tablets (old ASUS Transformer TF101 many years ago, and more recently ASUS MeMO Pad ME181C), and I've been very happy with them all. Even the TF101 is still in active use. ASUS is one of those technology companies I've grown to like and trust.
Leroux: Something you should pay attention to is the laptop's ability to remain aspect ratio. Sadly, this is not among the usual info you get, but I'm in a similar position - although I'm mainly looking for a cheap working laptop, I also want it to be able to run old games - and I've tried laptops that just didn't have this option due to their configuration and driver installations, making them useless to me in this regard. If you only want the laptop for retro gaming, it's even more essential that it can display 4:3 resolution like 800*600 or 1024*768 without stretching the image to weird proportions.
I haven't really found a better way than just trying them out in order to determine which laptops are better than others when it comes to offering the remain aspect ratio option, so far I can only say that a HP laptop I tried was the worst, while an Acer didn't pose any problems, but that may also have been incidental (dependent on other things than the brand) and could change from model to model ...
I'm like you (4:3 games should be displayed in 4:3), but I recall some here even wanting to stretch all their games to "full screen", with no black bars on the sides. :)
However, are you sure it wasn't about the graphics driver versions? I've had laptops with NVidia, ATI/AMD and Intel graphics chips, and all of them have displayed older 4:3 Windows games fine in correct aspect ratio, at least after I've updated their drivers up to date. Or are there some specific mobile graphics chipsets that just won't do it, no matter what?
I originally had some graphics issues with HP ProBook 6470b (could be they were related also to aspect ratio, but I recall it had a very limited set of resolutions available at first), but after I was able to update the graphics drivers to latest ones, my problems were gone.
Updating the drivers was a bit problematic though: the graphics drivers that HP offered in their homepage were very old, and when I found newer ones from Intel's homepage, they refused to install over the HP drivers. The solution was then to uninstall the original HP drivers first, and then installing the newer Intel drivers. There was some stupid fail-safe mechanism in those drivers that wouldn't install vanilla Intel drivers over customized(?) but older HP drivers.
Now I'm playing fine e.g. KKND 2 on this HP ProBook on a 4:3 aspect ratio, no issues whatsoever.