OK, I've got a couple of ideas.
Sacrifice: A fantastic game with an absoultely innovative storyline, and a fantastic game overall. It comprises so many aspects of games but was not accredited because it didn't sell. Congratulations to Shiny and Interplay for the fantastic game, it was only a shame that it didn't sell.
Giants, Citizen Kabuto: Another amazing game from a (proud to say) British studio. First person gaming with a funny and entertaining storyline, it was one of the games of the year in my opinion, as shown by it's magazine reviews. I loved it, and I think more people should have tried it.
The Red Alert Series: Undoubtedly the history of strategy legacy exists here, it really is one of the best - and most imaginative - storylines existent and is an entertaining series. I own them all.
Starcraft: The daddy of strategy, it was just a classic game that deserves mentioning wherever.
Planescape: Torment: What can you say? It shows what can happen with a meticulously designed storyline. You play it, you enjoy it and you experience the birth of a classic RPG.
Deus Ex: Can you not include this? It shows that an FPS doesn't need to have big guns to succeed in it's genre, the wealth of character options, solutions and fun is endless, you've got to experience it.
Freespace 1 & 2: The best star-based shooter in the world in my opinion. Action, storyline and big guns all in two boxes. The explosions rule.
Silver: A European attempt at a genre held by Japanese companies. It's undeniably one of the best games around in my opinion, I loved the storyline, even though it was old-school and typical you could still enjoy it for what it's worth.
That's more than a couple, sorry!