So far, what I admire the most is of course games from the Final Fantasy series. it really amazed me with the beautiful and detailed world design. In addition, the character designs, monsters and eidolons are constantly improving according to the theme of each series.
And... that's the whole alphabet! I skipped a bunch from Assassin's Creed DLC because some folks were playing it at the time and I didn't want to spoil. There's a few from games I've played since I started, too.