Bitcoin is the gold of the crypto world and will remain so for many years to come. It's going to be incredibly difficult to replace bitcoin.
As for Ether, I think it does have its own value even though it benefits heavily from airdrops and ICO's. I believe Ether has an edge over STEEM.
Despite all the platforms springing up on a regular basis, I believe steemit has built roots deep enough to handle anything. The userbase is strong and loyal, and there's a social heirachy that's evolved on the platform.
Let's not forget that steemit is mad fun. I see brigther days ahead for STEEM, competition or not.