Risk Legacy. This is a fantastic game. It did something no game before it has done and so far no game after has done. You literally modify your game permanently as you play through. You rip up cards, you write on your board, you put stickers on things. Added to that cool factor this is a very solid version of Risk. With a new victory point system games of Risk Legacy are done and over with quickly. We were often able to fit in two or more games in one night.
Eclipse. This one is still a newcomer to the scene but it's already found it's place at the top of many gamers 4x list. Eclipse is the perfect mix of simplicity and depth. It's a version of Twilight Imperium that can be played in a couple of hours. What it lacks in options it makes up for in gameplay and speed. Since getting this one I haven't touched any of my older 4x games and I don't really expect to go back to them any time soon. Added to that they just released an expansion to Eclipse adding ever more options and strategies.
3. Race for the Galaxy is a non-collectible card game and one of the best ones out there, sci-fi or not. It started as a re-theme of San Juan but has grown into a very solid game of it's own. It combines role selection with resource management and traditional card mechanics. It plays just as well with two players as with six. Fair warning though, there is a bit of a learning curve with this one. The cards use a ton of unique symbols to show what they do and these take a bit for people to pick up.
Star Wars X-Wing Miniature Game this is probably the most fun game I've played so far in 2013. Another newcomer to the market, it's quickly growing in popularity. X-Wing is basically a Star Wars re-them and re-write of the classic Wings of War dog fighting game. It combines simple to learn mechanics with a hidden movement system and amazing pre-painted models. There have been complaints about the price per model on this one but I find that this is actually one of the cheaper miniature battle games out there, especially when compared to Games Workshop or Privateer Press.
Star Fleet Battles this one has been around since the 70s and is still supported and played. Sure there have been some new iterations released. Mostly ones that make the game simpler and quicker. Games like Klingon Armada, Federation Commander and Call To Arms: Star Fleet. I figure if we are looking at best games of all time, I think the original deserves the credit here. SFB did hidden movement of ships long before Wings of War and X-wing and it added having to allocate your energy each turn to that. Having to decide just how much to allocate to shields, engines, phasers, scanners and more will always stick with me.
Alien Frontiers was one of the first games to come out that combined dice and Eurogame mechanics. Like games like Kingsburg, you start each turn by rolling a set of dice. Then the dice become your workers and the game becomes a worker placement game. Alien Frontiers uses this mechanic excellently with each die representing a ship and the numbers rolled determining where each ship can land each turn. Add that to a variety of way to earn victory points and a short play time and you've got a winner.
Battlestar Gallactica Here's one where I agree with the Forgotten DM. This is a great game. I see a lot of people who compare it to Shadows Over Camelot and I'm not sure that's totally fair. Shadows is a co-op game where there might be a traitor in your midst. To me Galactica is a team game because you know at least one person is a cylon and it's the humans vs. them. Half way through there's a great balancing mechanic that looks at who's winning and then adjusts the teams accordingly. Other than that it's a good game all around though a bit hard to explain to newcomers.
Space Hulk I don't know what it is but I love this game. I loved this game since it came in that box there on the left. I collected all of the Games Workshop 3D Roleplay games and Space Hulk was always my favorite. Awesome looking models combined with the epic Warhammer 40,000 universe and fluff combined with quick to learn but difficult to master rules. Things like the way blips work still seem brilliant to me and it seems like every mini game after it had rules for Overwatch.
Twilight Imperium Another one that's on the Forgotten DMs list. I know up above I said that Eclipse has replaced this one for me, and it has. That doesn't mean that TI needs to be dropped from the best games of all time though. This one is a beast, but it's the board game that does space exploration in the most detailed way. It's the closest you will get to playing Masters of Orion on your kitchen table. One caveat you have to have the first expansion for his one to belong on this list. Shattered Empires makes this good game great.
Battletech I have no idea how I forgot this one the first time around. I loved this game. I need to get back into this game. It's been around almost as long as I've been gaming and is still supported and played. Battletech is an amazing game of giant robot combat. It's crunchy, strategic and highly scalable. There's what seems like a near infinite amount of supliments out there ranging from new factions, new mechs, rules for tanks, jets and more. What's really cool is that behind it all is a great world of fiction rivaling the denseness of even the Warhammer universe. I still feel shame for forgetting this the first time around.