I have installed OpenBox on Linux Mint and it worked to 99% which was well enough but that was on an earlier version of Mint.

A little bit late but:

https://distrotest.net/

This is impossible to answer for 100% of people. Having said that i think the best place to start is Linux Mint.

Now if you are an ex windows user (which most here likely are as gamers) then the recomend for Linux Mint is even more suitable. You can also look at Ubuntu if Linux Mint turns out to not be what you are after.

Both Mint and Ubuntu have very active and helpful forums, and that counts a huge amount for troube shooting.

Having switched from Windows (except for games) a number of years ago i still consider myself a total Linux newbie, for example i nearly always use Mints GUI (as i would in Windows) rather than the UNIX favourite of the command line. Luckily Mint is enough like WIndows (pre Windows 8 GUI changes!) that getting around it in the GUI was a very easy shift to make in my transition from Windows to Linux.

So start with Mint, use it from a USB/DVD first (so not as an installed OS) to have a test run etc and check out the forums for any questions (or finding answers to questions):

https://forums.linuxmint.com/

If you have old hardware or a low powered laptop (my acer travelmate is a Centrino (Vista era!) cpu!) then go for Mint XFCE first. If you have current hardware try Mint Cinnamon.

Linux is not Windows and a number of key aspects are different enough it can't be a 100% smooth transition, however Mint is a great place to help in that transition and you can always move onto other distro's once you got your feet wet.

Of course it is impossible to tell what the best GNU/Linux distribution but here's what I can tell about my Linux experiences:

My first interactions with Linux have been half-hearted attempts messing around with Knoppix and OpenSUSE (which was on some magazine DVD). Late I tried Ubuntu but didn't really spend much time on it. My first distribution for daily use was Linux Mint Cinnamon.

Ubuntu LTS is a solid base for any distribution. As I absolutely despise Unity/Gnome for default mouse/keyboard usage I really appreciated the rather traditional approach by Cinnamon. In the long run I have encountered some problems which annoyed me quite a bit.

What I didn't like about Linux Mint:
- The update process of Linux Mint in general is rather unreliable and breaks sometimes until you fix the problem manually.
- Upgrades to new major releases (e.g. from 18.2 to 19) can be unreliable and and are hard to apply for Linux newbies.
- Too many outdated packages from a feature perspective. As a Windows user this annoyed the crap out of me.
- Old kernel versions have to be removed manually as they can fill up the entire /boot partition and block further kernel updates.

After trying out some more distributions via live USB boot I found Manjaro to fit my tastes.

What I like about Manjaro:
- Based on Arch (not using their packages though) and therefore comes with rather "bleeding edge" software, package updates are being released every few weeks (except for security updates).
- Rather easy to install and setup (uses the great Calamares installer)
- Excellent and beautiful implementation of Xfce (still using the Cinnamon community edition though).
- Since it's a rolling release distribution no major system upgrades required. Updates never broke my system so far.
- Very active community.

Overall Manjaro is surprisingly beginner friendly. Still, Linux Mint is a good place to start for those who are new to Linux.

I'm surprised no one has mentioned Antergos. It's basically Arch Linux with a GUI installer. It's a great way to get into Arch in case you want the system without having to go to the terminal so often. This is coming from someone who used Mint right before trying Antergos. I was pleasantly surprised how easy it was to get the installer up and running. It's an online only installer but there is an offline version called Portergos which is also portable, just like the name implies.

While you're allowed to use the Arch forums for any help, the Antergos forums are a little more lenient, I should say in terms of helping beginners. Especially ones who know nothing about the terminal.

I have so far used it for general use. Watching videos and surfing the web. Found really no problems with it, even after updating it. Had some minor graphical glitches which was quickly solved by the forums.

I was also surprised on the arch wiki and how thorough it is and how easy it is to understand when in the uncommon case you do have to go to the terminal. Much of it also can apply to other distributions of Linux.

Caveat, though that Arch is recommended to beginners with a grain of salt but in my experience as someone who came from using Mint for years, Arch seemed very solid and seems to be doing everything Mint does and more.

I appreciate all the responses! I've been tinkering with a few options that have been listed, and I think Manjaro has the most potential overall. Linux actually offers 90% of the software packages that I need, but gaming always seems to be the big issue for me. If I can't get GOG to run on Linux, then it would be pointless for me to switch. I've heard that it can be done through WINE, but I've also heard that it can be quite complicated to set up. I wish GOG would work on a Linux version of Galaxy.