I own Terraforming Mars and I've played Fallout.
Terraforming Mars is a great game with a tonne of expansions (it's kind of creaking under the weight off all the add-ons at this point if you decide to use them all in a game). It's for 2-5 players (there's also a solo variant). I think it's best with 3 or 4 players. The idea behind the game is that various corporations and entities have been given contracts to Terraform Mars and you want the group you control to be the most influential once the task is complete. This is done by increasing the planet's oxygen level and temperature, as well as producing oceans. Once those three parameters are maxxed out, the game ends. The game combines resource management/economy with area control/tile placement but the main focus is on the card driven mechanics.
At the start of each turn, each player generates 6 resources (money, steel, titanium, plants, energy, and heat) and adds (or in the case of money, sometimes subtracts) that from their stockpile. Then each player is dealt 4 cards which they can buy into their hand using money. Once that's done, the game turn, called a "generation" starts. Starting with the 1st player, you go around the table with each player taking 1 or 2 actions per round or passing. This continues around the table over and over until all players have passed at which time, the generation ends. The 1st player marker is passed to the next player and the process starts again.
Players spend their actions to conduct various actions, the main one being to play cards from their hand. Each card costs resources (mainly money but steel or titanium can be used with certain cards) and may have prerequisites or limitations (ie, you cannot play this card unless your energy production is at least 2/turn or more or, you cannot play this card until the temperature is -14C or higher). There are 3 types of cards. Red ones are single use actions (drop an asteroid to increase temp and get titanium). Green ones are also single use but you keep them face up after play so you can meet prerequisites later on. Blue cards also go face up and allow you to take special actions once/generation or provide a constant bonus (eg, spend 7 money to increase oxygen 1/generation or pay 2 less to increase you energy production).
Other actions would be to spend your plant resources to place a forest on the planet surface. Placing forests increases oxygen, earning you VPs Spend money to place a city or an ocean. Spend money to increase temp. Increase your energy production, etc. You can also spend money to buy awards (spend 8 money to earn 5VP at the end of the game for the MAYOR award. First person with at least 3 cities placed on the map may buy this award). Whoever has the most VP at the end (called Terraforming Points) wins.
I like it because there is a lot to do in the game. Each corporation has their own abilities and strengths and it's fun to try to figure out which cards and actions work best with those abilities. There are a huge number of cards in the game so there's a lot of variety. There isn't a lot of direct confrontation between players although some cards do allow you to attack other players. Plants are especially vulnerable to attack and you can wipe out another player's plant stocks via asteroid drops, introducing herbivores, etc. There's also some jockeying for good map tile placement and playing to block other players but the game is chiefly about efficient resource management and playing to your corp's strengths.
The downsides are few, but here they are. The component quality is a bit cheap and the artwork is functional at best. There is a lot of card text to read through and it can be a bit overwhelming for new players to remember what each card in their tableau does if they have a lot laid down in the late stages of the game. The solo game is not that good. It's basically a race against a turn timer where you have to complete all the objectives in 14 turns and much of it devolves to luck. If you don't draw good card combos, you'll fail. If you do get the combos, you should win as long as you understand the game mechanics.
Fallout
It's quite similar to Star Wars Outer Rim if you've played that. Very nice component quality and a lot of attention to detail. The game play is basically map exploration and a race between players to be the first to complete their winning objective (semi random based on which character they play. Each player draws a card with secret objectives on it based on their character). You explore the semi randomly generated map by moving from location to location and turning over encounter cards then resolving them through various means such as combat, skill checks, spending money, etc.
I enjoyed it well enough when I played but after just a few times playing, I noticed a lot of repetition in the encounter cards. For me that was the big issue. There weren't enough encounter cards and chances are you'd see ever one of them by the 4th-5th playthrough. Outer Rim initially had the same issue but fixed it with an expansion that added a lot more cards. I don't know if Fallout did the same.
