During all those I have been doing games now (since the early 90s), I wondered how I could convey a maximum of "experience" with the most simple effort.
Its not cause I am lazy (which I am), its rather because I like idea that not the big badda-boom stuff is groundbreaking, but the small ideas and gameplay innovations.
Blizzard for example is a company You can hardly call "groundbreaking" in terms of gamedesign.
They take an established idea, throw away the useless crap, and focus and enhance the core gameplay so that it makes You an additcted "Insert Your favourite Blizzard game"-player.
Lets not forget that it took them about 20 years to get there, back when the company was started they called themselves "Silicon&Synapse", and their main business was porting games. The experience they gathered through all their games is what You find today in WoW.
Now, if You look at gamedesign today, it still boils down to what makes games fun and worthwhile .
Why do we play ? Why not watch the grass growing, or do some outdoor sports, watch TV or read a book ?
The fundamental thing about games is that they offer a kind of reward compared to the effort, which You don't find elsewhere.Sports require You to go out, move, sweat and risk injuries.Sports are often affected by weather conditions, health conditions and the like.
Watching TV is a pretty passive, pre-built experience.Reading a book as well, although You can have Your fantasy paint the pictures that illustrate the story.
Watching the grass growing is probably something for the most passionate Zen-master.
Games require not much effort.You can play "Solitaire" by sitting at a table.
Games reward You with the illusion of having achieved something (like sorting cards).And people consider this fun.
Games can be rewarding beeing played alone or in groups, which makes them pretty flexible.
The thing behind it all is that You get something worth Your time, that affects Your senses and gives You the feeling of "achievement", which is absolutely subjective.
More advanced games not only give You achievements, but they add a story (like a book, but more active), motion (like some Wii games or the fact that Your reflexes are tested) and visual satisfaction (like watching a movie).
Games unify all the things that other media offer separately, into one big package.
Playing something like Mass Effect is like reading a story, playing the hero, train Your reflexes, improve Your coordination, provide a visual satisfaction, provide Your with satisfying achievements, offer "milestones" where You can say "OK, thats it for today, I finished that quest, tomorrow its a new one", which gives You that warm, fuzzy feeling that Your time and effort were met with a sense of accomplishment.
So, if You design games, what You need to design is basically a framework to provide any if not all of these things.Its all about satisfaction.That "makes" Your game.