"Warcraft II is one of those titles that suffers from having a CPU that performs too fast. Monkey Island Series, Kings Quest V,The 7th Guest, Doom, Quake, Diablo, Age Of Empires II, Warcraft II, Command And Conquer, and Descent: Freespace."
All of these games will work in DOSBOX, are on GoG or are on Steam already.
Age of Empires and Warcraft II will install on Windows 8 no problem. Quake probably will to, and I wouldn't be shocked if Monkey Island and Kings Quest install fine. I have Diable, The Sim 1 and Black & White installed on this Windows 8.1 box right now.
Freespace has an HD remake on Steam. WarCraft II Battle.net edition should also work fine on any modern PC and includes a number of fixes you'll probably won't want to miss.
Now that DOSBOX supports Glide emulation, you can get a lot running in there properly and looking fine, including Tomb Raider (also on Steam).
Any game that works on XP will work on Windows 8.1, with a little tweaking. I'd had people give me lists of games they could only run in XP and I had them all working fine. You might need to shim them a bit (compatibility mode, etc.), but they will go.
There are only two kinds of games I couldn't get working in Windows 8.1, that you will get working in 98SE/ME.
1. DOS games that won't work in DOS BOX for x reason
2. Windows games that are 16 bit won't emulate on 64bit Operating Systems (but will run in 32 bit).
Just my recommendations:
I recommend the biggest HD you can get. The ISO files take up a lot of disk space rather quickly. If you can find an old PCI IDE RAID card, you can RAID 0 two matching IDE drives and get a good performance boost and a bit more disk space. I am running 2 80 GB drives on one of my retro rigs, which runs Windows XP now.
Remember also that Windows 98 SE has a bug that does not support over 256 MB of RAM, so you are better off with ME if you are getting near 1 GB of RAM. You can get unofficial patches, but it still doesn't really use the RAM.
I wouldn't bother with Windows 95 because it simply lacks any method of troubleshooting. And you will be doing a lot of troubleshooting on these rigs.
Another thing I'd mention is that you are dealing with old hardware. Old harddrives, old soundcards, old ram, old videocards.
Keyword is old. You will have disk issues, you will have bad RAM. You need to thoroughly check these parts before using them. And they will fail on you frequently. I've tossed out half a dozen old videocards, from parts snapping off, to bad RAM, to failing when attempting to overclock.
Now you are hitting the wall here on Videocards: ATI, Nvidia or 3DFX.
ATI still has bad drivers. That's never changed, I wouldn't recommend them because it's difficult to find drivers and they don't support their cards as long as Nvidia has.
3DFX is good for games that are specific to Glide (Tribes, Starsiege, Mechwarrior 2, Quake, a few others).
Any game that fully supports Glide is going to give you a decent experience on a 3DFX card... Once you hit some of the later 90's games (Giantz: Citizen Kabuto, Tribes 2), the Voodoo3 will be destroyed.
...however, that being said, you run up to an Nvidia GT 6800 in Windows 98/ME, which will hands down blow away a Voodoo3 in Glide with OpenGL or DirectX. I've done a lot of benchmarking on older video cards, and on the old AGP slots, a Universal AGP FX 5950 was the best card I could find. Anything later, you'll need to make sure you have a newer motherboard for the later AGP 2.0 cards.
You can't really win with Glide anymore. The Geforce 2 and greater cards will greatly outperform Glide in any game. It was good at the time, but it looks awful and you won't get 1080p out of them. For a "Modern" gaming system, I'd go with anything FX or GT and you'll get old games at 1080p on a new monitor easily.
PCI is too slow for video and the BUS is shared, so you may end up with video, NIC, sound all sharing the resources.
For Processors, I found I struggled on a PIII 500 Mhz. If you are looking at chips in the 1 Ghz range, I'd focus on AMD boards at this time period. The early P3's were better than what AMD had to offer, but AMD was king up until the Intel Core2's came around, and the i-series took the performance crown. My second rig is an old Athlon XP Shuttle X system that performs with ME quiet well.
Drivers are a bit difficult too. Some manufactures are not updating the links anymore. ME does give native USB support, so you can plug a USB key and install the drivers, but 98SE does not seem to. You'll need to map a drive over the network or create an FTP site. That could tricky, as newer operating systems tend to reject their connections by default.