Guaranteed software updates.
Samsung has a habit of abandoning major software updates for its older phones. While it continues to support older devices with security updates, the new devices are typically the only ones that get the latest and greatest new features.
Meanwhile, Apple and HTC do a great job at providing software updates with new features for their older phones.
Get better apps.
To be clear, this isn't Samsung's fault. Developers tend to make new apps for iPhone before moving to Android. And when they do make Android versions, the apps aren't typically as beautiful or functional as their iPhone counterparts.
Apps are so essential to a phone's overall experience that I can't see myself making the switch until developers start taking Android as seriously as they to iOS.
Put more emphasis on Google apps, not Samsung apps.
Google makes some of the best apps for smartphones. Between Gmail, Google Maps, and the voice assistant Google Now, it's a great experience living in Google's world, even on the iPhone.
But Samsung tends to de-emphasize Google's apps in favor of its own apps for stuff like emailing and Web browsing. Samsung also has its own voice assistant called S Voice, which is far worse than Google Now.
Samsung would have to start making Google's apps and services the default before I consider switching.
Stop letting carriers install apps I don't want.
U.S. carriers have a lot of power over smartphone manufacturers. As part of their agreement to sell Samsung phones in stores, Samsung has to let the carriers load the phones up with a bunch of apps most people would never want to use. This "bloatware" lives on your home screen when you first power on a device, and there's no way to completely remove it from your phone. Annoying.
Until Samsung can do what Apple does and stop carriers from installing unwanted bloatware, I'm sticking with my iPhone.
Make a smaller operating system that doesn't eat up storage on the phone.
Samsung packs a lot of extra features into its phones on top of what comes with the basic version of Google's Android. But all those extras take up a lot of valuable storage on the device. If you buy one of Samsung's 16 GB Galaxy S4 phones for example, you have fewer than 10 GB to work with.
Apple's iPhone operating system only takes up a little over 1 GB.
On the other hand, I'm getting kind of bored with my iPhone...
I test a lot of Android phones, and almost all of them these days have bigger screens than the iPhone 5S, which has a 4-inch screen. My ideal device would be an iPhone with at least a 5-inch screen, but that doesn't exist yet. Rumors are swirling that Apple will launch two new iPhones this year: one with a 4.7-inch screen and one with a 5.5-inch screen. If that turns out to be false, I may suck it up and switch to an Android phone anyway.
A bigger screen would also mean Apple would be able to add a bigger battery. That would solve another gripe I have with my iPhone: The battery can't even last a full day. For now, I'm stuck using a Mophie battery case.