Until we get a true 3D X-Com, this excellent title will have to do.
It eschews the base-building component found in the original PC title, but the RPG elements of bringing characters along from mission to mission is still intact -- almost to a fault. Your main characters will always come back for each mission, even if they have fallen dead the previous round. It's a mild gripe, but the battles do lose some tension when you know that one of your men can take a sacrificial dive and still come back to life for the next heater.
Otherwise, all of the classic gameplay is here intact: action points, aimed shots, snapshots, the ability to reserve action points to lay down fire during the opponent's turn... the only missing tactic is the ability for your soldiers to kneel, both to take cover and to gain better firing accuracy. What's new is the ability to assign your characters' gained experience points to various skill branches so that they can specialize in traits such as stealth, medic, rifles, heavy weapons, etc. It's a nice way to add extra personality to each unit, in addition to building out a well-rounded troop that has multiple options when in the field.
Whereas the original X-Com games made you concoct a story in your own head for the soldiers that you were creating and controlling, Rebelstar gives you a prebuilt cast with a pre-built campaign storyline that is actually fun to play through, a la the Fire Emblem titles. Battles are fairly challenging with a good roster of locales and obstacles for you to work with. Add in the two-player, head to head battle mode and you have some serious shelf-life for the game.
I'm glad that the Advance Wars series has brought back the hype for turn-based tactical squad games. Perhaps more publishers will take note and move the wealth of gameplay ideas off of the handhelds and onto the PC and next-gen consoles where modern graphics, physics and online play can be brought to bear.