To be honest, the only one I've ever seen was "The World at War (1973)", and I'd like to see some more. Any good ideas? I'd prefer some with good factual in-depth information rather than being too bombastic and simplistic.

The World War 2 youtube channel is the best at looking at the war that I've ever seen. Everyone interested in history should check it out.

Yep, love how World at War has first-hand interviews with the people who were actually there.

I have to say, IMHO the World At War is probably the gold standard for World War II documentary series. To be honest, I've seen so much modern-day sensationalistic History Channel/TLC bombast that it's almost bled everything else out.

I do vaguely remember seeing Battlefield on PBS, and World War II: Behind Closed Doors from the BBC, both of which were pretty good. I've also heard a lot of good things about Blood Upon The Snow: Russia's War.

The Discovery Channel in Canada used to also air an aviation-themed series called Wings, profiling famous Allied aircraft, but it later branched out into Wings of the Luftwaffe (viewing the airwar from the German perspective) and Wings of the Red Star (which focused on some famed Russian WWII aircraft like the IL-2).

Finally, if you really liked The World At War and don't mind spending a bit of coin ($5.99 USD), I really recommend Hardcore History's Ghosts of the Ostfront podcast series, where Dan Carlin takes his very distinctive style of examining the human angle of war, and focuses it on the Eastern Front - each of his podcast episodes are several hours long. There's a great preview of it on YouTube here: https://www.youtube.com/watch?v=upAzM5Mduvw

The only WW2 YT channel I like is Mark Felton. It's very superficial but for me to enjoy a documentary I need to like the narrators voice, especially those very nice British accents which make the whole thing more respectable.

yep Mark Felton is awesome
I watch TIK for eastern front mostly he makes few political/economy vids too, mostly commie bashing:P

Mostly just going to second Mark Felton as a very good, professional source on youtube and the Battlefield series that was on PBS and the BBC. Battlefield is actually one of my favorites because of its relaxed, lecture like style of presentation (having watched lots of documentaries, a lot of the time they tried to be exciting on the level of movie which they never could be anyway). The individual episodes tend to be fairly long but in depth looks at individual battles (bearing in mind some level of redundancy and changing definitions of battle. E.g. the Battle for Russia encompassing aspects of other battles which will get their own episodes). Unfortunately, it's a little hard to come across the series (I own a couple Blu Ray and DVD sets of it) but somebody I recall posted most of it on Youtube with region locks on some episodes for some reason (that's easy enough to get around).

Another series I liked was WWII in Color. In spite of a lame name and sounding like it came out in the 1960s it's one I liked for similar reasons as Battlefield except it it is mostly chronological narrative on the conflict. If memory serves it is mostly correct, I can't remember what the one or two issues might have been but that's the problem with even the best documentaries.