Do you like Mass Effect? Sure, of course you do. It was a smash hit when it was released in 2007 and spawned one of the most popular franchises of this console generation. And now that Bioware is focusing its energies on Dragon Age: Inquisition, you're in dire need of a massive sci-fi game with action, exploration and branching conversations.
Well, do I have a game for you. The critically-acclaimed, but sadly oft-forgotten Star Control II.
Star Control II was developed by small team at Toys for Bob (read: two guys made the whole game) and released on DOS PCs in 1992 and later ported onto the ill-fated 3DO console. Never let it be said that I don't cover PC games or stuff on weird consoles. In 2002, the creators released the source code for the 3DO version onto the Internet, prompting a fan remake called The Ur-Quan Masters that is readily downloadable today. For FREE.
So from a monetary standpoint, this is an easy recommendation. But is it worth your time? As Star Control II is one of the best PC games ever, yes, it is worth your time.
As alluded to earlier, Star Control II is a massive sci-fi epic which throws together a ton of different genres and completely pulls it off. The overarching plot is about as basic as it gets. In 2135, Earth was enslaved by a group of very powerful, very antagonistic bug-like aliens known as the Ur-Quan. Unbeknownst to the Ur-Quan, a group of Earthlings had escaped and constructed a super starship on a distant planet. You are the captain of that ship. And now you've come back to destroy the Ur-Quan and free Earth and all that jazz with the help of a bunch of alien buddies.
After a quick opening sequence, you are pretty much free to fight the Ur-Quan and their legions of battle thralls as you see fit and are thrown into the galaxy at large.
And the galaxy is very, very large. There are hundreds of star systems that you can travel to, each with their own orbiting planets that you can harvest for resources. You can randomly explore and hope to find some friendly races. Or you can immediately plow into the middle of Ur-Quan space to try to fight them head-on.
PROTIP: Do not plow into the middle of Ur-Quan space at the start of the game. It is a poor life choice. And if you do choose to fight, you'll get to experience the pretty fun action portions of Star Control II, which are 2D, top-down dogfights. They're perfectly adequate and quite enjoyable once you get the hang of them, but fighting isn't the main attraction of the game. The exploration and conversations are.
I mentioned the exploration a bit before. You'll fly around the galaxy and find planets which have resources which can be traded back at Earth to upgrade your ship, get some escort fighters, or replenish fuel and crew. And of course, you'll find aliens races. Lots of alien races. This is where Star Control really shines. All the aliens are completely different and they are all completely memorable. As finding them is part of the fun, I won't spoil too much, but your encounters will include a race whose translators don't work correctly -- so they speak in Engrish -- a race of sentient blobs that have extensive knowledge of bioengineering, and a race of weird mushroom ... things that worship a concept called Juffo-wup.
You meet and learn about these races in branching conversations that are informative and humorous and provide extensive cultural and societal data. The level of detail put into each race is quite staggering when you consider that this game is more than 20 years old.
Star Control II was a game ahead of its time. It wasn't content to create a world. It created a galaxy and filled it with things to do and people (or reasonable equivalents thereof) to meet. It's an epic quest that really feels like a spiritual predecessor to Mass Effect and worthy of its lofty status among gamers. If you still aren't convinced, then maybe one more piece of information will push you over the edge. I once gave this game my ultimate endorsement. I named a fantasy baseball team The Ur-Quan Masters. If that doesn't convince you, then nothing will.