When GTA3 came out, and I was in awe. I didn't think anything like that would ever come out, with massive improvements over GTA1 and 2.. Yet, despite the new and enhanced sandbox play, I was... kinda bored after a while.
The reason? I played Ultima 7 first.
An old computer RPG released in 1992, this game offered unprecedented freedom at the time. It was real-time and all NPCs had a schedule, offering an immersive world. When it's night time, (most) people go to bed. During the day time, people go to work. You can even follow people to see how their day goes, and in one side quest you follow the mayor and find out that he's having a affair. You know what game hyped up scheduling nearly 14 years later? Yeah, tri-Ace's Radiata Stories.
The interactivity was deep at the time, and maybe even by today's standards. Do you want food? Just go to the farm and kill the cow. Or buy some flour and make bread. You can even forge your own sword, play musical instruments, change the diapers on babies, participate in a carnival. You can even rob the national mint at night, break into weapon shops and steal their goods, and so on.
And you can kill (almost) everybody. My brother was very liberal with this. Outside of one of the care shelters, these little kids run up to you and play tag. My brother tagged them, alright. He tagged them with his sword. He also murdered everybody in Britain and formed a road of bloody corpses leading up to the king, naming it Bloody Road. His crowning achievement was when he brought a powder keg (a medieval bomb, if you will) into the bar during peak hours and blew it up, taking 4 or 5 people with it.
With interaction like that, GTA3 was miles away. "You can have sex with a hooker, then run her over and get your money back!"? Pfft. "You can kill the Mint lady, rob the Mint of its gold bars and gold nuggets, and then resurrect the woman to exchange them into usable gold coins." Now that was cool.
If you can find a copy, and haven't played Ultima 7 before, give it a try. It's been remade with an engine called Exult
to be playable on modern systems.