I can only imagine what Apple would be today if Steve hadn't been taken so early.
I think that it would be similar to today's Apple but some of it would have happened sooner. Steve Jobs' gift was in his ability to look ahead and anticipate where things were headed way before anybody else.
Getting the big differences out of the way, Apple would still be a far more secretive company, holding its cards close to its chest and giving few to no outside interviews with vague answers when contacted by the media. I actually think that Tim Cook's open Apple was an improvement over Steve's handling of the company. Also, I'm not sure Steve's priority would have been user privacy, a Tim Cook bet that has been paying off in spades because their primary competition — Google — cannot ever match it because their business model depends on profiting on user data. Non product business decisions like these weren't Steve Jobs' strength, though Tim Cook or others under him would have probably steered him in that direction anyway.
The Apple Watch would have still been the next big thing after the iPhone. I just think that Steve would have gotten to where we are sooner, skipping over the Watch Edition fumble, sold as a computer on your wrist rather than so much of a focus on fashion and absolutely not releasing the Apple Watch 0 which in retrospect was unusable. It just would not have been released in that state, even if it had to come out a year later.
Apple and Disney would have been much closer than they are now and rather than creating an AppleTV service, Steve would have worked in tandem with Disney to release what's now becoming Disney+ and it would have been tied to Apple products, maybe even an exclusive to AppleTV as Steve wasn't a fan of working with competitors. Recall that Steve protested allowing iPod+iTunes on Windows. He had to be convinced and of course it paid off and was instrumental in making the iPod, then the iPhone the worldwide phenomenon they became. While a Disney + Apple partnership would have been massive, I think that Tim Cook's lack of emotional attachment has allowed AirPlay and TV+ on competitors' TVs and other devices, and this is going to be the right choice in the long term by making an Apple service widely available, leading to future hardware purchases.
Steve was obsessed with quality control and in the few times Apple slipped up under his watch (i.e. mobileMe), he's brought the company in line and back on track. The butterfly keyboard issue would have caused Steve to go thermonuclear. I don't think it would have gotten this bad nor would it have gone on for this long.
Scott Forstall and Jony Ive would have both had a long future ahead of them at Apple. Other executives who hated Forstall might've left. Jony's obsession with thinness would have prevailed and we might have had a paper thin iPhone by now at the cost of battery life. I think that skeuomorphism would still be around but iOS would still have been redesigned and more modern. Steve's primary directive was always in making things dead stupid to use and skeuomorphism was the way it was accomplished.
Finally, the big one that never happened: Steve Jobs was hyper focused on making conversational computing a reality. He would never have let his eye off the ball on Siri in the way Apple under Tim Cook allowed it to happen. Siri had an enormous head start over the competition and Tim Cook let not only Google, but Amazon take the lead and then become entrenched with consumers. Tim now realizes this and has been investing heavily into AI, ML and Siri itself. Siri will eventually get to where Steve would have taken it but I think that we'd all be having full fledged, natural conversations with Siri through our Watches and AirPods by now.
Ultimately, Tim Cook was the right CEO at a time of huge growth for Apple, guiding it to being more of a mass market company than a niche, though Steve Jobs' vision for what was around the corner and obsession with getting things right would have been valuable.
