Today I realised that I'm a sucker for additional free content for a game after release.

Two examples:
I really enjoyed Giana Sisters: Twisted Dreams, and Black Forest Games published extra Christmas, Halloween etc. levels for the first one or two years after release. Much later they even added a new game mode that fans had requested.
I really, really liked all of that. It made me feel like they cared even after I bought the game.
It was also partly the reason why I supported Black Forest Games' later kickstarters.

Something similar happened with Long Live The Queen.
I also enjoyed that game a lot and quite some time after I bought it and had played it, there was an update adding a bunch of new content that was really good and that I'm playing through now.

And now I wonder:
Am I feeling good about something that I should have already gotten when I bought the games? (Although delivering GS:TD with the seasonal levels already installed might have looked weird...)
Or is it OK to be happy about extra content that I get for free after release?
Does it show that devs still care about the game and don't directly move on to the next project?
Or is it all just a trick to make me (the customer) feel good? (And I totally fall for it.)

I'm not talking about patches and such but about extra content, stuff that gets added to the game.

It always makes me happy. Look at FTL. It got a great free upgrade.

You forgot to mention the most obvious examples: The Enhanced Editions of the Witcher games.

Didn't Postal 2 get a huge thing like this pretty recently?

I didn't forget, I just don't know anything about it. :-D
So, the Witcher games all got extra free content later?

The original Trine game got redone using the Trine2 engine... Haven't checked it out personally, but seems promising...

Yes. The upgrade to the Enhanced Edition was free for everyone who bought the game before.

Link 1, Link 2

I know what you mean, you like the free content... but is it right to? The dev's spent time and effort on the content, be it more levels, maps or what have you, and their giving it to you for free...

A game I dearly love, Nation Red, was released in 2008 and still gets updates to this day all for free! online co-op, guns, maps, modes, leaderboards, achievemnts, all this stuff added for free.

I like it but... I do feel bad that the dev isn't making money off the man hours he's putting in... so I don't know haha.

Guildwars back in the days, Terraria quite recently, those were great surprises.

yup - thanks for reminding me i need to download it in some cases, that additonal content expands the sale-ability and lifetime of a game way beyond what it would have otherwise. for a small studio / indie, that can turn a game from a one time success into a living - im pretty sure FTL and Postal 2 have seen sales boosted by the added content