In terms of Parks and Resorts from a worldwide perspective:
After the disappointing start of Disneyland Paris and the death of Frank Wells, Eisner's/Pressler's regime underinvested in new parks and attractions, resulting in huge cuts to AK's plans, DCA 1.0, WDSP, and HKDL. These projects included going against fundamental Imagineering principles, such as a lack of emphasis on placemaking (in DCA and WDSP), disregarding whether the outside world is visible from inside the park (especially DCA), inclusion of off-the-shelf rides (DCA), under-budgeting for new attractions, a huge brain drain that sent some of WDI's greatest minds to the competition, among other problems.
Iger started his tenure by immediately ending the "stategic planning group" that was cutting budgets on new attractions, and investing heavily into the incomplete/low-quality parks that were opened by the prior administration: 1.1 billion to fix DCA and hundreds of millions for WDSP and HKDL. Those investments were first priority because of the actions of the prior administration. If those had been full parks from the beginning, Disney would have been much more likely to invest more of that in WDW. But those parks were apparently viewed as emergencies.
There is much to discuss about things like the merits of SDL (I can understand how they viewed it as necessary to get a second chance at entering the Chinese market before it was saturated), the emphasis on IPs throughout the parks (I would prefer more original content), the quality of NFL (I wish it had one E rather than two Ds), price increases (to keep the revenue up while Disney catches up on development that will increase actual attendance), magic bands, etc. However, to me, it seems that Iger's biggest influence on the parks has been the reinvestment in opening major, high-quality attractions and immersive placemaking, even though I wish this trend had arrived at WDW sooner.
(Of course, this is a simplification that excludes details such as the role of Staggs in various decisions, the current placement of Chapek and whether it will mark a backslide in some of these things, etc.)