Testing some games on Eltechs would be a great idea.
cI very briefly tested Alpha Centauri, Anno 1602, Panzer General II (both GOG versions) : they both seem to be working, although Alpha Centauri looked a bit slow. I had a graphical glitch on the "welcome" screen of PGII, but had no other problems during my short test run. Anno was running alright but sound was a mess (lot of Alsa underrun messages from wine, maybe because emulation is too slow).
A few Windows 3.1 games and 2D games for Windows 95 or 98 should work, although quite a few games from the 95-98 era are still DOS games (and GOG seems to only sell the DOS version even when a Windows version was available), so they probably won't work with Exagear (Regular Dosbox on the PI 2 is already pretty slow as it is).
Examples of games available on GOG that could be tried :
Age of Wonders I
Infinity Games : Baldur's Gate I and II, Planescape Torment, Icewind Dale I.
Call to Power I and II
Capitalism Plus and II
Conquest of a New World
Disciples Sacred Lands
Dungeon Keeper I and II
Europa Universalis I and II and For the Glory : number II and For the Glory might work with a Pi 3.
Fallout 1 and 2
Lords of Magic
Imperialism I and II
Knights and Merchants
Heroes of Might and Magic I, II, III : I think GOG only sells the DOS version of the two first games though.
Master of Orion II
M.A.X I and II
Might & Magic VI, VII, VIII :
Return to Krondor
Panzer General II
Zork Nemesis and Grand Inquisitor
Concerning games not available on GOG, Civilization II should work great on the Pi 2 and the Pi 1. I wouldn't have high hopes for III. Diablo I, Railroad Tycoon II, Starcraft, and Warlords III might be playable on the Pi 3 (and maybe Diablo on the Pi 2).
The brilliant free King's Quest I, II, III and Quest for Glory II remakes from AGD Interactive are also worth a shot.
EDIT : the latest version (1.6) of Exagear Desktop for Pi 2 seems slower. I'm not sure if all the games tested previously (Caesar III and Pharaoh for example) would work as well as they had before.
EDIT 2 : added a few games.