I suggest you give Linux Mint or SolydK (KDE version, from SolydXK project) a spin in the VM.
Comparing Linux from 2000 to now, is like comparing huge first Motorola cellphone to smartphone.
Because Linux kernel started as unofficial UNIX clone for x86, it had minimal support from hardware manufacturers (small amount of hardware it reliably supported), small community and very little automation.
Due to kernel and GNU effort, ecosystem developed pretty fast. Then big things happened around 2010-2014, with AMD and Intel producing open drivers, with mesa project, with systemd (target driven daemon control), pulseaudio, kde4 (now kde5/kde framework in the work), git, ext4/btrfs, hal->udev migration etc. Also steam support, then GOG and desura. If you remember /etc/fstab - its only for static mount points today.
Strictly saying, today user does not need to know all this. Just grab a distribution that is binary and uses stable release cycle. Of course, there are other types (ArchLinux(+Manjaro,NetRunner,Chakra), Gentoo/Funtoo (+Calculate, Sabayon), Exherbo, and many others) - distrowatch.com search engine is pretty helpful for finding some new.
With wine, which is free implementation of winapi for unix-like systems (it binds the library and system calls to guest os versions), Linux supports around 70% of all windows applications. Modern Windows supports around the same amount due to legacy incompatibility, where with wine one can simply use other binary version where application has less problems. For this I suggest using PlayOnLinux (gui wrapper around Wine) or similar.
Dosbox, yes - all titles are supported.
Graphics hardware-wise, today all depends on manufacturer and type of driver. Problems may happen only on very old hardware (nvidia and amd), or very new if its AMD. Never used two-chip notebooks, there is a way to switch them, but I heard its not so convinient. OpenGL support is not a problem anymore. One problem still persists heavily - its multigpu (crossfire/sli) for games, since those require special profiles.
Wayland is coming soon on desktops..
I jumped around 2010. I first used Solaris in 2008, but at that time Linux was boring. Then Vista happened and I tried Ubuntu 8.04 first time on VM.
From my point of view, the problem with Windows is.... that there is misunderstanding.
Windows is a "for consumer product". Its ... not an OS, its a platform from MS for commercial solutions. That means, not everything is allowed and there are specific agenda over which only MS has control.
Linux (GNU/Linux actually) is the universal OS. There are a lot of projects that intersect and build on top of it and each other, but finally, what it really is - depends solely on distribution channel picks. And that means, if you have ways to change something you want, it can be changed.
edit: gog forums glitched nicely