Seeing as this series is on sale right now, I'd like to ask which game in the series would you personally recommend for a newbie to this. About the only similar game I really ever played was "The Nations", about a decade ago. Thanks!

2 is a great starting place, and is considered by many the best of the series. I suggest you start here.

Anniversary edition is 2 remade in 3D graphics. From what I've heard (haven't tried it myself), it's true to the original, with some slight modifications. Still I suggest you begin with the original 2; it has aged well.

3-4 use a different engine, and different rulesets. People used to 1 and 2 found 3 and 4 to be different. That said, I played 3 and found it a pretty decent game.

I would probably go with 2 or 4 (as it's an improved 3). I find the feel of gameplay quite different. With the paths and soldiers only sitting around in towers 2 seems a lot more static to me, while the free movement of settlers and armies of 3 and 4 go for a bit more dynamic aproach.
However the main features of the series to me are the economics and to observe your people building everything up. This is given in all installations.
I go with 2 (remake, haven't tryed original version yet) when I'm feeling like lean back, watch them build and optimize transport routes and I go with 4 if I want a more dynamic feel and clashing armies.

I recommend Settlers 2 10th year edition. It's a very good remake, and the game looks great in 3D. The newer Settlers feel like a different game entirely.

I've just installed 10th anniversary.

Funnily enough, I think that the remake looks worse than the original, which has phenomenal graphics up to this day. I love the original. The anniversary, from what I can tell after an hour or so, has some slight modifications, but I would recommend to play the original. It looks better.

It also has them sexy screen frames.

Thanks all, I think I will go with 10th anniversary.

Good choice. There are fewer buildings and more tool tips. It's a good place to begin the time sinking journey ;)

For any people stumbling across this thread in the future: definitely get the 10th Anniversary Edition instead of the original Settlers II. The combat in the original can become a total slog, dragging out a mission and making it very unfun. The remake alleviates this by giving you the option to upgrade existing military buildings and also allowing you to kick all the soldiers out a building. This makes it easier to direct your troops to the frontlines and also has the benefit of not wasting your precious gold coins (you can kick fully trained troops out and then have them replaced by rookies). It doesn't solve all the problems with the combat, but it helps so SO much.

I enjoyed Settlers II when it came out and enjoyed the Anniversary Edition a couple years ago. I have been replaying the original since last week and the nostalgia is the only reason I'm sticking with it. I just had to restart a campaign mission five hours in because I was in a position where I would have rely on catapults to stand a fighting chance and it would have taken several hours more to gain the upper hand (even with the speed up cheat, which is prety much essential).

I like the road-building in Settlers II but I can totally see why they gave you full control of your units from the third game on.

By units, do you mean every single unit, or just military?

IMO the best game in the series is Settlers 7, it's really a modern game with refined game mechanics and very good gameplay. I know it's not on GOG, but for me, it's the best of the series.

I just got (thanks KingBradley) 10th Anniversary myself. Will be giving it a try soon.