All time favorite game would be... Ultima VII : The Black Gate (Forge of Virture) + Serpent Isle (Silver Seed). Best game eveeeeeer.... so far anyways.
After saying that though, I haven't played it through in like 10 years or something... Am I just being nostalogic to a childhood game?
Nope. It is *that* good. Comprehensive dialogue, huge detailed world, moreso than anything I've played since; you can do practically anything you want in the world; huge long story (one of those games you Really can benefit from a strategy guide, since you'd probably never find ALL the secrets without it...)...
It's kinda like the perfect MMORPG, except everyone's in character; and you are the star of the show. Although a few weakness', Cave Story has probably about the same number of songs as this 100+ hour game... [but even without constant music, it works. Thanks to enviromental SFX, you're never left with the impression of empty sound space...]
The biggest weakness would be the graphics. STRONG then. Very awesome GFX when it came out. These days it's on par with Cave Story GFX. So take what you will...
No game has recreated a world quite as comprehensive since...
(The game had its own language, its own lengthy history, NPCs that ate, slept, went around doing whatever job they do... Day to night, ships, flying carpets, horse and buggy(?)... You could follow the storyline, or just wander aimlessly. Cast Armagaddeon and end the world, or make it rain for fun... Fight dragons, or try to conquer the kingdom you are protecting... Anything you want to do~
...
I might say other games are my favorite today; but as for All-time favorite game. It would have to be that.
"Yes... rest and heal... so that you are strong and able to face the perils before you... Pleasant... Dreams...."
"You'd best not do that Avatar!"