28. Mass Effect

Mass Effect created a great universe full with great characters and with an amazing lore. The quest to hunt down Saren was one of the best I ever played. It is easy to overlook the few flaws of this game since the complete package is just so good. 

My game nr. 26. has to do with making some light towers shine.

27) Civilization V (PC / 2010 / Turn-Based Strategy)

Endless hours of fun, offline and online. More replay value than 99.9% of games. It may be repetitive, but it never gets boring.

26) The Elder Scrolls IV: Oblivion (PS3 / 2006 / Action RPG)

Like Civ 5, repetitive, somewhat generic, and not terribly well designed, but engrossing like you wouldn't believe, and you can put in hundreds of hours without ever wanting to stop. It's an interactive world of which you are a part, and almost without equal in that regard.

Hint for 25: Conspicuously absent innuendo. Sort of the beginning of a series, but not really.

#26 - Populous: The Beginning (PS1)

The game that got me into the Populous series, and one of the later Bullfrog works I played (but one of the best), Populous 3 was an odd beast.  Part God game, part RTS, but a whole lot of awesome, the whole range of resource management mixed with defending and attacking plus the shaman powers really made for an awesome entry.  Still  more than playable to this day and absolutely unique, a shining beacon of Bullfrog at the peak of their influence.

Clue for my #25 - Sequel to a Quake mod which became one of the most popular online FPS games of all time, still played to this day.  Hats.

First Smeags posted Skyrim, then Kantor with Oblivion. It seems we're going back in time through the Elder Scrolls...

26. Elder Scrolls III: Morrowind Game of the Year Edition (PC, also on X-box)

This game just shows why the Elder Scrolls series is considered one of the best WRPG franchises in existence. A wonderful open world that's truly unique in it's art-style and architecture; cities made from the carcasses of giant crabs, nomadic tribes, mechanical ruins and a range of natural scenery caked in ash from the Red Mountain. As soon as you get off the boat there is just so much to do, so many skills to learn, places to explore and guilds to join. The music is also fantastic. Jeremy Soule created a fantastic soundtrack that has been tweaked/remixed for later games yet still stands strong as a brilliant collection of music that perfectly evokes all the emotions felt whilst playing an Elder Scrolls game. The gameplay may be a little old school for modern tastes, but there is an immense depth to this game that should not be missed.
 

One of the best open-world RPGs ever created.

It seems like 26 is a good number for the Elder Scrolls series.

Someone better have The Elder Scrolls II: Daggerfall as their #26!

Clue for 25: A certain mods avatar...

Donkey Kong country, gotta love Krankys Kabin :D

edit . scoobes hint - Sonic and Knuckles?

Team Fortress 2

as for populous that is such a great game, but for me the SNES game will always be the best of the series given it stole so much of my teenage life playing it :D