Up until recently, these other blockchains held an advantage over Steem because of the lack of Steem blockchain based tokens that Steem projects could use to reward users, investors, contributors etc.
Indeed the success of Steem DApps to date is even more impressive than it appears because of this handicap.

3 weeks ago, this handicap was lifted, and boy has it been liberating!

Wait a second @apshamilton - Steem tokens existed long before Steem Engine. I even had a token tutorial up 3 months ago here

Even before that there was the Pocket token which was kind of buggy and not really working well which used comments: https://steemit.com/pocket/@biophil/pocket-announcement, but I wouldn't consider this what DApps were looking for in terms of ease of use to create and to use.