I relate it to the show Supernatural. I found the first two seasons very interesting with their hunting of various monsters. The third season kept my interest as the demon theme took precedence over the show, and I manged to keep up to the end of the fourth season when Sam was tricked into raising Lucifer from Hell. Well, after that it started getting harder to watch as, wait for the epicness to unfold, Sam was destined to be the vessel of Lucifer and fight his brother Dean who is prophesied to be the vessel of the Arch-angel Michael. Some of my friends liked this story, but it felt painfully drawn out to me, and the story no longer had any of the 'lesser' creatures that I had started watching the show for.
I prefer stories that are rooted in the world with believable chance of occurring. Sure, you might have to fight an evil drow army to get to the gates leading one of Orcus' netherlairs so that you can shift the cosmic balance to the side of good again. But you can also do that fighting a tribe of gnolls that have over hunted their area and are turning towards the small village of Homlet for the next food source. I prefer to have little victories, hard fought battles, and well earned trophies. The group I am currently GMing is playing a group that is averaging 3rd/4th level after 3 years. Now, the group has not been playing non-stop for the last three years, and there have been some character deaths have set back the average party level, but everything their characters have, has been earned. No-one is tossing another '+1' sword in to their collection of magic items to be sold at the next town and the story of the group has begun to transcend into old ionic. And that sir, is how I feel it should be done.
On a side note, a scenario that I would truly consider old ionic is to run two groups, unbeknownst of each other, on an adventure, in parallel, with opposing goals. The adventure ends with the two groups meeting and 'battling' it out to see who is the victor.