All the below games are old and already out, but they are worth noting if you haven't given them a shot already.
http://www.youtube.com/watch?v=hnKPns54Uso
Empire at War and Force of Corruption is a solid RTS with the Star Wars spin, but what makes this game awesome is the xer0x mod out there that some dude who must REALLY like Star Wars made. If you're a SW fan, you should be able to pick up Empire at War with the FoC add on for about $10 - $20 on Steam, maybe $5 - $10 if you wait for it to be on sale. Before games stores became completely obselete, I found this on a shelf one day at EB and got some serious entertainment value and mileage out of a $10 pick up.
http://www.youtube.com/watch?v=16cYAo8NypI
If you've ever played Heroes of Might and Magic and Enjoyed it, stop wasting your time and money on that crap and play King's Bounty. Again, this is a game you can get the entire trilogy on sale on Steam for about $10 - $20 and you'll get 60+ hours out of each of them. It improves on a lot of things, mainly by making it real-time rather than turn based, and fairly open-ended. If you like this style of game, then you should give this series a long look.
http://www.youtube.com/watch?v=Nc3oE7Kkdg0
I was pleasantly surprised by this game, which is an effective RTS / RPG hybrid. It is a bit older, and the graphics are a touch dated, but if you like RTS and are intrigued by the idea of an RTS with a solid backstory and heroes who expand, upgrade and have inventories and a level system akin to an RPG, this is also worth a grab. Again, find the Steam sale for $10 for all the titles and expansions if you're a bargain hunter.
http://www.youtube.com/watch?v=64xS0pKa7Ek
If you like the City-Builder type of game Tropico 1 - 3 are a must-try. The first has an incredibly addictive side to it despite being about 8 years old. The sequel "Pirates Cove" changed the dynamic a bit, but is still quite challenging as well as entertaining if you like the genre. If you want something a bit more polished and "with the times", then Tropico 3 and 4 are probably more your cup of tea. The music and voice acting are definitely less epic and more annoying, but the graphical improvements are there while the gameplay is still pretty solid all around. What's not fun about being a dictator of some Banana Republic in the Carribbean, especially when your "Tobacco" crops look incredibly like weed in pretty much every installment of the game I've played. Have political enemies? Shoot them. Arrest them. Interrogate them and assassinate their children. This game definitely carved a niche for itself by being unlike anything else I've ever played as far as overall gameplay and options are concerned, while still having a pretty straightforward and yet unique City-Building feel.
Oh, and when that annoying advisor gets on your nerves, in the 3rd and 4th installments, you can shoot the bastard. Gotta love it.
http://www.youtube.com/watch?v=3TwMVM9ajwk
They just don't make `em like they used to. While the new remake of this game was fuckin terrible IMO, this game has a monster replay value and ambience that I haven't seen the likes of in years. The voice acting is boss, the inter-characters interactions give it a sense of challenge and personality. and it has a surpring entertainment value. This game has, believe it or not, consumed 260+ hours of my life over the past 5 years, though some of that involves having left the game running while I did other things.
Couple this with the fact that a smartphone could run this game, and you have the best $5 I've spent on a video game in years.
I know none of these games are new and are FAR FROM the "Latest and greatest" in technology or graphics, but they are a few gems I've discovered over the years that produced incredible gameplay and value at an often dirt-cheap price. If you're a game afficionado and you love finding those "Diamond in the rough" games that most people have never heard of or just didn't give a chance, the titles above should tickle your fancy.