Personally, I don't think that people's complaints with Epic levels stem so much from the (admitedly weak) mechanics in the ELH, as much as from the utter lack of anything really "epic" to do.
When I think of Epic adventure, I envision quests to save entire planes of existance, world-spanning dramas where every decision the players make has an immediate and dramatic affect on the entire universe.
The problem is that the ELH doesn't give us that. It just gives us more ways to kill stuff and take its treasure.
Granted, that "stuff" is bigger and harder to kill, and yes, the treasure is bigger and better too.
But when you boil it all down, it's still just Orc & Pie on a much larger scale.
Orc & Pie isn't epic in any sense of the word, no matter how big the orc, or how immense the pie.
Now, I've used the ELH rules, and they have served perfectly well for continuing beyond level 20. But our Epic games weren't Epic because of anything in the ELH. They were epic because the players took ownership of their characters, made them come alive, and got involved in the bigger picture.
Conan wasn't epic because he killed bigger critters with a better sword. He was epic because he dared violate the sacred temples of dark gods, and walk forbidden paths.
He was epic because of his personality and deeds, not because of his skills and powers.
Sadly, there's not really any sure-fire way to add that kind of epic to a game. That has to come from the players working with the GM to create a game that is more than just a bigger dungeon with more loot. It takes characters that are more than just a +5 vorpal sword, with the armor of the holy dingus.
Epic is about scope, not scale.
Bigger, better, faster, more is not epic.
If I were to design a revised ELH, I'd probably leave the mechanics of epic levels exactly as they are.
But I'd be sure to add some of the following to the book too:
Building a Nation - Now that you've tread the world beneath your jeweled sandals, it's time to wear that heavy iron crown. Let's have some rules for running a country. Warfare on a large scale, courtly intrigue, and economics.
Spearheading a Faith - You are the mightiest servant of your divine patron on this plane. Clearly you are the perfect figurehead for your church. What does that entail? What epic worship services will you handle? Will you become an avatar? Can a mere mortal truly channel that much divinity and remain unchanged?
Healing Mother Earth - As an epic character attuned to the natural world, what does your druid or ranger now focus on? It's not enough to just slay dangerous creatures that threaten the balance, there are other forces out there causing problems. You want epic druid/ranger/nature challenges? Check out Princess Mononoke. Or even Naussica.
The Big Job - You're the best thief in 100 generations. You've stolen the eye from deadly sacred idols, and risen through the ranks to lead a thieves guild. Now what? What's the next big score? How do you lead a thieves guild? Can you expand your criminal empire? When is enough money enough? Can a rogue ever really retire?
Epic Magic - Being the greatest archmage of all time is about more than creating a "Hellball" spell that does more damage. Real power comes to the spellcaster who manages to "bottle fame, brew glory, and even put a stopper in death."
Something like that is a lot more like my idea of epic.
(Not that it would be remotely fair to get two in a row, but I'd love a copy of Elements of Magic: Mythic Earth.)