Well, this would be easy pick, Hollow Knight, right? I do find it best that came from Down Under (sorry, BioShock was only co-developed there).

Except, I read Hobbit around '81...and then in December '82, The Hobbit, graphic adventure game made by Beam Software, released for ZX...I didn't have one, but good friend of mine had, and I was camping at his house quite a bit in those days. That game changed how I look at gaming, which was mostly arcades at that time, and introduced me to wonderful world of adventure games genre. Two Lord of the Rings adventure games followed few years later.

Generally speaking, Beam Software were quite prolific - looking at their list of games, I recognize many games I've played back then.

Honorable mentions go to FRAMED 1/2, Fruit Ninja, Flight of the Amazon Queen and The Forgotten City.

I just had to...

Bioshock, by far

Co-developed by Irrational Games Australia/2K Australia.

I don’t claim it as much as some Australians, but there certainly are a lot of Australian references sprinkled in like the little sisters calling big daddies “Bubbles”.

I’d mostly give credit to Irrational Games/2K Boston, but let’s say a 62/38 split with most of the credit going to the main USA, but the Aussie studio rounding it out into something fuller with their additions.

I can’t see the [directed] by Ken Levine comment any more, but I think it’s important to acknowledge the many creatives involved.
BioShock would have been much less interesting B movie schlock with less interesting story and characters without the many other creative contributers.

No doubt about it, but BioShock is quite a Ken Levin game - he's a Looking Glass alumni, so to speak, and it shows in BioShock.

I find L.A. Noire to be extremely underrated. It might have some flaws, but what a unique game! I’ll take it over RDR 1+2 and GTA 5 any day.
It even has a pretty good story.

However, Hollow Knight is such a masterpiece, so I have to go with that.

Easily BioShock - one of the best games ever made.

While it's not a showstopper like Bioshock or LA Noire, I'm gonna give a shoutout to de Blob 2 for being a really charming and fun little platformer and one of the rays of light in the dry latter years of Wii.

I agree I also forgot how many great Australian produced games are out there. SSG (Strategic Simulation Games) with reach for the stars widely regarded as putting  4X games on the map, who also made Gold of the Americas, the Warlord games and Fallout Tactics: Brotherhood of Steel.

Lets not forget Melbourne House/ Beam Software/ Khrome etc that gave to me my favourite Dreamcast racing game LeMan 24 hours - Shadowrun snes - The Hobbit and way of the exploding fist to name a few.

Medieval Total War II was iirc made in Queensland, it came to mind because I remember the editor of Hyper Australia's biggest selling multiformat game magazine left to go work on it for Creative assembly Australia. 

That's just a few Australian developers adding all those other games mentioned by our fellow VGCharters in the thread, and the many more that are invariably missed in endeavours like this increases our realisation of how many great games came out of here, so I will end by mentioning one of my favorite Australian produced games and that is irrational games Freedom Force.

Pandemic is, to my knowledge, American company.