A lot of story for a simple side-role: Rogue Trader
In the role-playing game Rogue Trader, you play as rogue trader, one of the subjects of the Imperium with nearly unlimited power – at least outside imperial borders. As a cRPG, the game features classic turn-based combat, isometric perspective, and a lot of story with various choices and endings.
Space Marines do not often appear here, but when they do, they are all the more impressive. A Space Wolf can act as your companion and introduce you deeper into the lore of the Chapter. This gives you a better insight into what Space Marines really are … and why their food is deadly for humans.
More importantly, however, Space Marines function as enemies in the game, as you encounter Chaos-corrupted Astartes at several points. Rogue Trader thereby presents something that you cannot experience so closely in any other game: how deadly Space Marines can be if you had to face them in battle.
Whenever a Chaos Space Marine is among the enemies, you can expect a really tough fight. You will probably only survive that because you rally an elite team of fighters around you, including a Magos of the Mechanicus, an Inquisitor, or an Adepta Sororitas, who could nearly match a Space Marine on their own.
Depending on how you behave, you can even gain further insights into the past of the Astartes and the reasons why some of them turned against the Emperor.
If you are not just looking to feel like a Space Marine, but want to learn more about their background and their importance to the lore as a whole, Rogue Trader is a good starting point. A “successor” for the game is also on the way: In the new role-playing game for Warhammer 40,000, you are not a genetically engineered superhuman, but equally dangerous