These are all free on Android, and are all awesome and replayable. A little downloading might be required for a couple of them (ScummVM and VCMI), but the rest work out of the box or with free and legal downloads.
Urquan Masters (Star Control 2 remake)
UFO:AI (Xcomish)
OpenTyrian (The best shoot 'em up ever)
Destruct! (Scorched Earth mini-game in OpenTyrian)
FreeCiv (Civilisation 1/2)
FreeCol (Colonization)
OTTD (Transport Tycoon)
Pixel Dungeons (Roguelite)
Slash'em/Nethack/DCSS (rogue heavy)
Free heroes 2 (HoMM2)
VCMI (HoMM3!)
Open Panzer (WW2 strategy)
Age of Strategy (TBS lite)
ScummVM (All the LucasArts adventures)
RetroArch (All the emulators in one, saves screen space).
A few decent console games for emulation (kind of in order of version preference in brackets). Probably a greyer area than abandonware because you can't get original copies easily these days. So, I'd download them just as like, umm, a "trial" of your tablet's capabilities. Then delete them for sure. In a few years. If you remember.
Pirates! (NES/SNES/Mega)
Simcity/2000 (PSX, SNES)
Civilisation (SNES, PSX, for proper top down nostalgia)
The rest of the Sim-type games (SNES, NES)
RotTK (SNES)
M.U.L.E (NES)
Herzog Zwei (Megadrive)
Ultima 4 (Master System)
Phantasy Star's (Megadrive, MS)
All the Final Fantasy's (SNES, NES)
FF7 (PSX)
Rampart (Megadrive, NES)
California Games (Master System, SNES, Megadrive)
Brutal Sports Football/Hockey (Megadrive)
Madden NFL 199x/200x (PSX, SNES, Megadrive)
PGA Tour 199x (Megadrive, SNES)
Tiger Woods Golf (PSX, GBA)
Worms (PSX, Megadrive, SNES)
Star Control 1 (Megadrive)
Syndicate Wars (PSX)
Magic Carpet (PSX)
Space Hulk: Blood Angels (PSX)
Final Fantasy Tactics (GBA)
Advanced Wars (GBA)
HoMM1(GBA)
The Pokemon games (GBA, GBC, GB)
Diablo 1 (PSX, use a different emulator than RetroArch)
Gran Tourismo 2 (PSX, different emulator again)
Smack down 2 (PSX)
Tekken 3 (PSX)
Command and Conquer (PSX)
XCom (PSX)
There are a heap more, but this lists at least a gazillion hours of playtime and replayability alone, and all work on my cheap little Huawei phone, so any Android Tablet worth its salt will run them better, and in a bigger screen format. Might want a keyboard or a gamepad for some of them, might not.