I want to play an RPG!!!!

Avencast?

Avernum?

Baldur's Gate?

Gorky 17(Haven't gotten it to work yet)?

System Shock 2(It's pretty RPG-like)?

And that's all of the 'old-school rpgs' in my rpg category.

Gothic 1 & 2
Two Worlds
Risen
Dragon Age: Origins
Witcher 1

Those are pretty good old-school-ish and really fun games. Gothic especially belongs among my all time favorites.

Edit: I don't play isometric RPGs, so I can't help you on that.

Hm, how is that that I don't see neither Arcanum of Steamworks and Magic Obscura
nor Fallout 1-2 ?
Eschalon 1-2-3 also
maybe Inquisitor too
Divine Divinity 1 too.

Anything by Spiderweb Software (Avernum, Avadon, Geneforge) has a ton of content, isometric view, and is a grid style turn based strategy rpg.

Here are a few good ones.

Fallout

Fallout 2

Fallout Tactics

Fallout 3 (Not Old School but Still Good)

Fallout New Vegas (Not Old School but Still Good)

Wasteland 1 (The Classic)

Divine Divinity

Beyong Divinity

Divinity II

Wizardry 6: Bane of the Cosmic Forge

Wizardry 7: Crusaders of the Dark Savant

Wizardry 8

ToMe (Tales of Maj'Eyal)

Dungeons of Dredmor

Geneforge 1,2,3,4,5

Expeditions: Conquistador

Rogue's Tale

Shadowrun Returns

Shadowrun Returns: Dragonfall

**Non-Steam Games:

Stonekeep

Neverwinter Nights 2

Vampire The Masquerade Redemption (Fantastic)

Lands of Lore 1

Lands of Lore 2

Syndicate

Syndicate Wars

Planescape Torment

MODERN TBS ISO
Blackguards
Shadowrun

RPG LITE ISO
Shadow Watch
Expeditions Conquistador

OLD RTWP ISO
Plansecape Torment

OLD TBS ISO
Betrayal at Krondor
Jagged Alliance 2

Play Fallout, just give a try and if you can stop, good for you!

Dragon Age is a good choice although not isometric, FallOut1+2 are iso, and VERY good games though the mechanics of FO1 are not as good as. ALso try Arcanum and Planescape Torment, though I did not like the latter

RPG FPS: Borderlands

Since your list includes the second chapters, why not trying Baldur's Gate+Tales of the Sword Coast and Icewind Dale+Heart of Winter?
Planescape: Torment is said to have one of the best plots in RPGs.

Did you played the expansion for BG2, NWN1 and NWN2?

Star Wars: Knights of the Old Republic is the best SW game, and also one of the best RPGs.

Arcanum.

At steam sales I bought Witcher 2 and Skyrim, very good RPGs. Witcher 32 hours ( completed ), Skyrim 29 and still enjoying it

From the top of my head, Divinity: Original Sin, KOTOR and The Witcher 2.

Shadowrun returns with Dragonfall, Arcanum, Fallout, Knights of the old republic 1+2, Wizardry 8 and some other i guess :)

Classic Fallouts and Planescape Torment, that's all you're missing.

Try NOX, it's not on Steam, but it's a great RPG! Shame not many people know about it.

Alright let me suggest some games I haven't seen on this topic yet

Epic Battle Fantasy 4

Septerra Core (might need some patches)

Now for the non Steam games

Venetica (is greenlit on steam but for some reason not published there)

Monster Girl Quest (if you don't mind "a little bit" sexual content)

And if you download an emulator like ZSNES you could play some classic RPGs like

Lufia

Final Fantasy

Bahamut Lagoon

Chrono Trigger

Super Mario RPG

Golden Sun

Terranigma

Breath of Fire

Fire Emblem

I hope I was able to help you.

Dark Messiah of Might & Magic

All of the above (many great games), and: Vampire: The Masquerade - Bloodlines | Anachronox | Summoner | Evil Islands | Drakensang series

Definetely The Witcher: Assassins of Kings!

Divinity: original sin, thats all you need!