Playing anything via virtualbox is... rough. If it's a DOS game, try dosbox or something similar. If you really need DX... whatever win98 used... then setting up a very specific Wine instance is the way to go.
If you're serious about the nostalgia, then your best bet is to find a 32-bit processor and build a dedicated win98 system. ISOs are available everywhere, most with updates and a disabled registration system. You might even try a 2k or XP system. Win2K was my gaming system of choice for many years, thanks to its backward-compatibility.
Hmm... well, VMWare used to make a virtual desktop app that was far superior in the way it handled DirectX apps, but I don't know if they still have/support that.