Not the Flash type games you get on sites like Kongregate but strategy games like Illyriad, (Pictured) Though you can waste an awful lot of time playing them. The web is an excellent platform for certain of multiplayer games. Heck you can even play games like Quake III which was a desktop game but redone using WebAssembly.
I used to play a strategy game Inselkampf (German for Island war) where you start off with one island and improve it then you can start building ships and invading other islands. I remember getting to the point where I was managing an empire of 80 islands and the only way I could do track all the details was with an Excel spreadsheet. But it was a big time hog, taking up over and hour and a half each day (just mad!) and I stopped playing.
It seems to have closed down a few years ago which is a shame as it was very popular in the mid 2000s. The UK website inselkampf.co.uk just has a start Game Over message on it! Searching about I even found a copy of the Inselkampf rules online.