You wouldn't say Apple has as strong or a stronger hold on the music and mobile phone markets?
On mobile phone markets, definitely not - last I checked Android was dominant there.
I can't say about the digital music market - if I had to guess, Apple is probably #1 there with iTunes, but not to the extent where they can control it.
There's plenty of adequate competition for search engines. If nobody else even knows about alternative search engines, you can't really hold Google liable for that, can you?
You can if they are shown to have abused their dominance position, e.g. by using tie-in to promote their other products, or by excluding their competitors. It doesn't really matter how they've gotten into that position in the first place, the damage is the same.