I'm also curious as to what some of the "bad" he did to the company. I only know how the parks were to visit when he was running them and they certainly aren't the same now.
Well, each one of them is certainly up for debate, but general criticisms include (strictly post-Wells) ...
1. Letting Katzenberg leave to found Dream Works.
2. Halting Disney's America.
3. Misunderstanding the European market and over-saturating EuroDisney with hotel rooms that sat empty.
4. The systematic dismantling of Future World.
5. The changing of "EPCOT Center" to Epcot '94 - beginning what I would term the "gimmick over quality" era of the company.
6. Hiring Michael Ovitz.
7. Purchasing the California Angels.
8. Building the 4th Gate at WDW.
9. Underfunding the 4th Gate and pulling the Beastly Kingdom money at the last minute.
10. Allowing a "land" full of carnival rides like Dinoland USA.
11. Underfunding the 2nd Gate at DLR.
12. Allowing two "lands" full of carnival rides like Paradise Pier and A Bug's Life Land.
13. Hurt the relationship between Disney and the Jim Henson Company.
14. Closed 20k Leagues - replaced it with a Jungle Gym.
15. Created hard ticket "events" where your regular park ticket wouldn't get you in.
16. Curtailed hours of operation in the parks.
17. Allowed Direct to DVD sequels of Disney Classics library.
18. Allowed Pressler and Harriss to let Disneyland fall apart and wreck the resort's relationship with it's annual passholders and local fanbase.
19. Opened DisneyQuest - let it fall apart do to lack of updates/maintenance.
20. Closed/changed many classic attractions.
21. Built/removed Alien Encounter (either way you look at it, one of these was a mistake).
22. Wrecked Adventureland's themeing with the Magic Carpets.
23. Allowed Princess-ification of World Showcase.
24. Turned too many table service restaurants into Character meals.
25. Changed Meet & Greet model into static location; instead of roaming characters.
26. Refused to pay for maintenance and upkeep on EPCOT Center without a sponsor paying for it.
27. Sold off land in Orlando.
28. Introduction of the Disney Dining Plan.
29. Introduction of Fastpass.
30. Allowing the over-reliance on generic "Disney Parks" merchandise and the shunning of land/ride/resort/hotel specific merchandise.
31. Letting Main Street turn into one long department store.
32. Destruction of Pleasure Island.