People like analogies. Two regular comparisons on HN and elsewhere are Windows vs Mac and iPhone vs Android (interestingly the second is also used as an analogy for the first).
All of these analogies are wrong.
A smartphone has very high (what I call) built-in utility. You can use it to make and receive calls, send and receive SMSs/emails, take photos, get directions and browse the Web. At a guess, this accounts for probably 70% of smartphone usage. A large portion of the rest would be (again, I'm guessing here) games.
Android is a commoditizing product. With the standard Google apps, you get 70% of the utility (based on my earlier assumptions) of an iPhone. The point here is the ecosystem doesn't matter as much.
The iPad is a different beast entirely and (as I've been saying for 1.5+ years now) IMHO much more important and will be a much bigger market than the phone market. It will (and already is) cannibalizing a lot of PC usage and sales.
The thing to note about the iPad is that 70% figure is (at least anecodtally) vastly different. The ecosystem matters. Apps and content matter much more than on phones. And this is where the iPad competitors really suffer and will continue to suffer.
It's why I have the most hope for Amazon in the iPad competitor space because they have the closest thing to what the iTunes ecosystem can provide. Without this, despite the relatively low price, I don't think the Kindle Fire would've sold anywhere near the number of units than it did.
A better analogy for the iPad than the iPhone is actually the iPod. 10+ years after the iPod's release it still accounts for the majority of MP3 player sales. Yes you can rip your own CDs and buy your MP3s from Amazon and elsewhere but the convenience of the ecosystem trumps pretty much everything else. Last year it was rumoured that Apple would kill the Classic until it was pointed out that the Classic is the fifth biggest selling MP3 player (the top 4 are all Apple too).
Apple's supply chain management, innovative financing and unprecedented warchest certainly have given it a massive advantage, no question. No one else can (yet) create a product at similar specs for a similar price. But it's the ecosystem that has driven and will continue to drive the iPad's dominance.