If you judge depp on the past 5 years or so, yeah. He got rich, had kids, and decided to do pirate movies. That's ok. I'm not raged.
But if you look at the body of Depp's work he's got a few things going for him. He's picked smart scripts. That's not acting, that's just having a good agent and a discerning taste. But that alone sets him above the pack when it comes to actors. The other thing is that he changes his mannerisms from script to script. That's something that, not being an actor myself, seems to be at the core of acting. You can't change your face or how long your arms are -- but there are things within your control which you can. It's something that so few actors seem to even attempt to do.
Depp and DDL are the only two (popular) ones that I've noticed even trying to do it.
You could say that DDL has never stepped out of his comfort zone, where the career of Depp has been wide and varied. I wouldn't say that makes DDL less than Depp, or Depp better than DDL. It just makes them different actors. Both of them are probably as good as the generation has to offer, but for different reasons and in different ways.