I'm looking to buy a real-time strategy game from gog, but i've just recently got into PC gaming and didn't have a chance to play all these games back in the day so I don't know what's good.
I'm thinking of maybe getting Earth 2150 or Earth 2160. I kinda want to avoid RTS with a fantasy setting since I already have the turn-based HoMM 3, but other settings are fine. Any other suggestions for a good RTS buy from gog?

Sadly, GoG doesn't really have any good RTS' that I like. And I like ALLOT of RTS'. The closest you can get that I reccomend is more of a base building sim called Evil Genius. Otherwise, people here like Empire Earth, (I hate it :| )

Original War is awesome. Just... Just get Original war with it's branching story, interesting setting and original game mechanics and you'll be happy.

Its not on gog but if your looking for a great rts you couldn't do any better than total annihilation. Its like 10 bucks from impulse. I haven't played many of the rts on gog so i couldn't recommend any of them besides homm 3 which you already have.

I second the vote for Original War. Though the story involves time travel, the vehicles and play style seem realistic. It's the only game I've posted a review for and my avatar is from the game.
Ground Control is a tactical game mostly. Also futuristic, you start with a set of units and finish the mission with what you're giving, no resource gathering whatsoever.
Sacrifice, though it has a weird, fantastic setting, is not your average fantasy with elves or goblins but with all new creatures and involves collecting souls and it's pretty different from other games.
I've bought 2150 but haven't played it yet.

Hmmm, Original War didn't quite interest me personally, but I might try a demo of it and see how it is.
As for Ground Control, I like gathering resources and building bases, so that's out.
Thanks for the suggestions though.

Earth 2150 (the second one? could be 2160) is pretty good but i just wished it wasn't that early 3D where everything had a lack of detail. But the continuation of your base and the changing climate of the dying planet does make it a much better game than other RTS's of the day.
In Original War you can train apes to do your bidding! Well fetch and carry stuff, but still it's a great game with a funky, b-movie plot. You may not like fantasy but Warlords 3 is a fantastic rts with a lot of style and depth.

Hostile Waters - More squad based than full scale RTS. But pretty unique with a good story.
Earth 2150 - One of my personal favourites. The only downside is it will leave you wishing its features were available in other games too.
Imperial Glory - Kind of like a cross between Shogun and Empire Total Wars. But pretty good in its own right too.
Original War - Also squad based but definitely worth considering.
Soldiers Heroes of WW2 - pretty tricky, but better than most WW2 games.
You're right, that's 2150. Personally I think that it hold up quite well, graphically. Especially given how badly most games of that era have aged.

I smack your b-movie head! It's based/inspired on/by a book! One of the best german sci-fi!
*mumly* ...ja tem sracum ukazu poradne becko...*/mumly*

Hostile Waters is the best recommendation I can offer, if you don't mind it being an action game too.

I agree. I had never heard of it until it came to GOG, and I bought it based on recommendations from other forum users. I have rarely been so positively surprised by a game.
Regarding the Earth series, I found Earth 2140 to be basically unplayable, and 2150 was barely an improvement. I found the interface to be clunky and needlessly unintuitive. I haven't tried 2160 yet.

if you planning on having any online activity whatsoever with your game that you decide to get. Then don't buy from GOG.

I swear on what used to be Uruk's soul that this is the best, most hardcore RTS involving WW2 on GOG.

I really love Sacrifice. Completely new take on strategy game genre and it still feels fresh and new even today. Haven't played any others, I'm not a huge fan of 'older' RTSs.

*ducks*
Leave my b-movie head alone! I use it to watch MST3K!