Divinity: Original Sin
Divinity: Original Sin 2
Pillars of Eternity
Pillars of Eternity II: Deadfire
Tyranny

You can get Divinity Original Sin Enhanced Edition from the Gog community giveaway now. There are five copies.

Baldur's Gate and Icewind Dale are the games Pillars was trying to emulate and fell a little short, in most opinions. That's a good place to start, with BGTUTU or the BGTrilogy mod on the classic games, or the Enhanced editions. Great games either way.

You could try Spiderweb Software games (Avernum, Geneforge, Avadon). If you are *really* cheap, you could get plenty of hours of play just from the shareware/demo versions of these games. (The demos have other uses, of course, like seeing if the games will run on your system (handy if you need to use WINE), or determining if you'll even like the games before paying for them.)

What specifically are you seeking to replicate in those in cheaper alternatives?

There's plenty of classic RPG games: Baldur's Gate 1 and 2, Planescape Torment, Fallout 1 and 2, Icewind Dale 1 and 2, Neverwinter Nights 1 and 2, Dragon Age: Origins. These are the best.

- long gameplay
- replay value
- good story
- no fancy engine ( can run on my potato pc )
- mod support (?)

In these regards I think nothing can beat Neverwinter Nights. It's very debatable whether the official campaign can be considered as a "good story", but the good thing about NWN is that it doesn't just offer mod support, but module support, meaning you can play loads of freely available custom campaigns that are more gripping and better written than the official content. If you can run it on your potato PC and you're fine with the graphics and gameplay in general, you'll have an almost endless supply of good long stories with huge replay value.

That's too euphemistic. ;-)

Rocket League and Broforce.

Dwarf Fortress
and
UnReal World

aint no flashy GFX

but meat n' Taters in spades on the cheap as free

*raises an eyebrow*

+1

right?!

Try Planet Alcatraz, game available in steam. But not fantasy setting, more for fans of Fallout.

Beyond divinity and divine divinity. Earlier and cheaper games from the same company.:)
Also you might be interested in
Temple of elemental evil
Lionheart
Gothic and risen series