Some video games I've put alot of hours on:
Red Alert: Tons of fun: I maxed out though with downloading scenarios. THey are a ton of fun though.
Prince of Persia: Alot of fun, but the browser version has no savegame function, and one mistake can make you restart the whole level.
Imperator Rome: It's alot of fun. But a single play through can take maybe a month. And to turn on Achievement mode, you aren't supposed to be able to reload older save games from before your last savegame. So if you make a mistake, you can't go back further than 1 savegame. It also has a lot of micromanagement, so I got overwhelmed by Achievement mode.
Men of War and MOW Assault Squad 2: I beat all the Single Player official missions, but multiplayer matches take awhile to set up with a friend (you need to get a friend to play this outdated game) and matches can last a while.
World of Tanks was very addictive, but it was also monotonous, with tons of "grinding" to get new tanks.
Battlefield 1 and 5 were great, but the single player missions do't have much replay value, and after a while the multiplayer modes start to get old.