Please suggest both post-apocalyptic and other ones. looting, fps/tps + rpg hybrid, atmospheric, open world and non-linear. I have Borderlands series, and it feels like Fallout 3 (in some aspects). Any recommendation?

Hmm, well there is brutal legend, which is open world, but its a linear story, and no shooting or stuff like that. VERY atmospheric, as its set in a heavy metal world.

Stalker series and Metro series.

If you have bought a few games during the sale you should have a copy of STALKER Clear Sky. It is open world with a fairly open world to explore, people to meet and a world to hunt in. It meets most of your requirements and also has weapons and armour damage scales too.
The story is fairly inlier but I personally really enjoy the STALKER games and I would say they have enough in common with Fallout 3 for you to enjoy them. (Clear Sky is the second best after CoP)

The closest is probably stalker. It's not an rpg, but it feels a bit like one and like Fallout 3 also has a huge, fairly open, game world.

There is the S.T.A.L.K.E.R. series. They're post apocalyptic FPS games set in a zone based open world. Although there isn't a skill system, there is a lot of side quests, dialogue options etc. The overall tone is a lot more serious and well...(as silly as this sounds) realistically post apocalyptic than Fallout 3/New Vegas, and the atmosphere is untouchable. The combat is also a bit tougher as both you and the enemy can go down in a few hits and you can't just point your weapon and expect to hit 100% of the time.

Just to share a little experience: I had defeated some bandits and was going through my inventory trying to throw out what I didn't immediately need (as your weight affects your speed and stamina), it was late at night and I couldn't see more than ten feet in front of me. As I'm standing there a mutated beast came out of the shadows and began feeding on one of the bandits. One of the few moments in gaming that legitimately scared me, ha.

For another little moment: I was working my way through an underground maintenance tunnel, fighting a few bandits that had made it their home, when a large monster suddenly lets out a scream, becomes visible and charges at me. Another moment that startled me and made me want to be anywhere but where I was.

Well, I don't know your tastes (older or newer games), but Fallout 2 with Restoration project is a must!
+ Fallout 1
+ Wasteland 2

Rage is sort of similar and a very underrated game to boot.
It's a bit linear but the shooty bits are very good.

The all-mighty Fallout 2.

The first time I ran into the ghouls in the tunnels really scared the crap out of me.

I'll 'second' the Stalker series - esp. Call of Pripyat. All of them are 'open world' (although not one single 'continuous zone' - there are 'zones' - but they are large and you can travel back and forth between them), and you have a lot of freedom in how and when you do things (and to go do your own thing and ignore the 'main quest' for a bit if desired).

There are also a ton of 'full campaign' mods - that will give tons of hours playing more and new stories in the 'exclusion zone' (that's where the story takes place).

Very open and fun RPG'ish FPS. One of my favorites.

As far as the Metro series - I only know the one here on GOG; Metro Last Light. I picked it up on on 'day one' here on GOG (based on how much I love Stalker) - and to be honest - have more or less lost interest in it - it seems to be a 'corridor' game, very linear, with plenty of QTE's, and not 'open world' at all from what I can tell.

By 'corridor', I don't literally mean 'it's all in corridors'. There's outdoor areas and so forth - but each area seems to be a self-contained 'mini-theme-park'. You cannot go back and can only go forward the way the story propels you. For example - you get guided to an outdoor location - and while there can only just do the task told to you (like 'kill the three thingys'). No real exploration - no going back and coming back later. No going forward until that 'task' is done - then you are 'propelled' along to the next mini-them-park. Each area also seems to have a 'you went thru the magic unmarked 'next-zone' door - and now it's locked behind you - you can't go back - even if you weren't done looking around (and tragically - that same door 'model' is also used 'in-zone' so you can't really tell when you are facing one). Metro has been very linear so far - way more than, say, HalfLife - where you could at least tell you were going to 'zone' and could wait an complete your area checkout first. Unfortunately I've found it disappointing, so far.

Definitely look at Stalker :)

Thanks guys! :)

Haven't tried it yet but Convoy looks pretty good and describes itself as a 'tactical roguelike-like inspired by Mad Max and Faster Than Light.' Customize a bunch of vehicles and explore the wasteland to find the parts to repair a spaceship.

http://www.gog.com/game/convoy

Metro / Stalker like the others
and Rage is not bad