Neverwinter Nights 2 had some solid tools for campaign building that were the closest I've seen to creating a world with scenarios like those you see in DnD. It helps that the game was almost literalally DnD, but still impressive.

I don't think DM'ing is necessarily fun though. Most everyone I know who DMs sometimes, including me, finds it to be pretty stressful and a lot of work. The real value to me, is that a really good DM knows when to break the rules to enhance the game experience, and how to do it without making people angry. They create scenarios that specifically challenge the characters that are playing, not just for combat, but for role-playing purposes. Ie, a Lawful wizard is tempted to steal a scroll that would contain the knowledge he seeks the most, or a cleric who must decide whether to uphold her team's plan to ally with an unscrupulous NPC, or to go rogue in the name of their ethical code and deliver justice to said NPC. Good storytelling and cooperative play is just something that comes very naturally to some people, and having a human in the loop to respond to events in the context of an overarching narrative and party experience is really hard ot beat.