First you need to define "open". Open in what way? Open source code? Open API? Open as in sharing your personal data? Open as in telling you about how it's sharing your personal data? Open as in data portability? Open as being honest about its business plan? Open to ideas? Open to being open? etc.
edit: generally speaking, so that I don't seem like a complete douche and give you some form of answer rather than answering you with a bunch of questions, Google "feels" more open than say, Apple or Microsoft, but that can be because of good PR.
edit: generally speaking, so that I don't seem like a complete douche and give you some form of answer rather than answering you with a bunch of questions, Google "feels" more open than say, Apple or Microsoft, but that can be because of good PR.