Is it possible to restart a PhD due to issues with supervisor (and should I do it)?
Adding a student's perspective to Pete's answer:
My advisor told me at the being of my master thesis, that soon I would know more about my particular area of research than him. At the time I didn't believe a word he said, but at our third meeting I was already explaining stuff to him and by the fifth I started to feel irritated that I had to explain stuff to him which I didn't have to explain to his PhD student whom I collaborated with.
But then I realised that I worked on this topic all day every day, my collaborator worked on a related topic and discussed my research with me several times a week but my advisor only got to spend time on this topic every other week when we met with him, because he had plenty of other students to advise in the meantime and also had his own research, teaching and some administration to do.
So from the sixth meeting on it became a habit for me to open the meeting with a quick catch up on my topic and my progress before diving into the details. And from that meeting on I always got great advice from him.
I think you need to think about whether you have given your advisor a fair chance to help you when you were stuck and whether he has been able to help in that regard, because that's his job and knowing all the details about your current topic is your job.
Switching from one thesis supervisor to another is hardly a "rebellion". In fact it's a fairly common thing: in my own PhD program it seems to happen roughly 5-10% of the time. (In institutions with a higher rate of faculty turnover, it is probably more common.) And switching advisors is much easier than any form of "starting over a PhD". You should definitely look into this: starting by identifying some other faculty member in your program that you think would be a more suitable supervisor, and see if they are amenable to research-related discussions.
Your claim that your advisor "really is incompetent" is disturbing. I am a bit skeptical of it: not necessarily through arrogance, graduate students often have unrealistic ideas about faculty knowledge. If you walk into my office and ask me a question about something, maybe I can answer it right away and maybe I can't. But if I can't it might still be in one of my papers! Being an expert is much more about knowing how to find out important information / solve problems eventually than about what can be summoned at a moment's notice. In general I feel like I am fairly helpful in providing information to others in a professional context, but I have had the experience of people who for whatever reason simply don't wait a reasonable amount of time for me to answer their question. I remember one person in particular who would ask me a question cold, and after less than a minute of my thinking about it, he would say "Never mind" and move on to something else. That was rather frustrating: what kind of question is important enough to deliberately ask someone else yet not important enough to wait a few minutes for a good response?
Another point is that there are levels of expertise. Most faculty members are regional, national or global experts on something; but that thing or things may not be what they are teaching in all their courses or even what they want their students to work on. One of the hard parts of the advisor/student relationship is to find a topic of mutual interest in which the advisor's expertise is strong and can be appropriately conveyed to the student. Oftentimes this requires some patience and several tries: most of my students have not written their thesis on the first thing I suggested to them.
Anyway, though I may not want to, I have to admit the possibility that there are truly incompetent faculty members supervising PhD students. That sucks. If you feel this way about your advisor that's more than enough reason to look for a new advisor. But I think that in practice you should keep this to yourself as a reason for switching, at least until your thesis is approved and you are ready to move on to your new job. To have an incompetent tenured professor is only possible through some alarming combination of enabling / incompetence / total lack of contact or oversight on the part of the other faculty in the department. Fixing that kind of problem is above your pay grade.
Added: Though switching to a different faculty member in your department is easiest, it need not be the best choice: there may or may not be another suitable advisor in your current department. It's quite possible to transfer from one PhD program to another: doing so need not be (and probably will not be, unless you promote it this way yourself) a failure or rebellion. If you have only been in your current program for a year or two, you could plausibly start fresh elsewhere. If it's been more than that, you may want to look into the possibility of arriving at another program with advanced standing, up to "ABD status". Also, (especially) if you are American and studying in Europe, maybe consider coming back to the US, especially if that's part of your post-PhD plans. I mention that because coming back to your native country provides a sort of implicit explanation for your change of programs: many fewer questions will be asked of you.
It's true that switching advisers might be difficult, especially within the same department. There are a few other options:
Make do and finish your PhD nonetheless. Remember a PhD is supposed to be an open-ended research work on a challenging topic. It means that many things are not going to work, that the end result cannot be perfect and, importantly, that your adviser cannot hold your hand and lead you to a guaranteed solution like instructors in bachelor or master courses. It's difficult to judge how serious the situation is from the outside but some level of frustration is quite common and you do need to manage your expectations (if your adviser has time for you and is happy to sign off on your work, you are in a better position than many PhD candidates…).
Seek a secondary adviser. For better or for worse, it's actually quite common for professors to oversee theses on a broad range of subjects and exercise only minimal supervision, relying on junior colleagues to deal with the details. In some cases, the secondary adviser can also be a full-professor at another university. Ideally, he or she should complement the first one and help deal with some specific aspect of the topic the latter knows less well. This could help you get guidance on some important aspect of your work you feel your current adviser is not competent to deal with. But do clear that first with him before approaching others.
Switch adviser. Yes, it's difficult and politics often make it almost impossible within the same institution but it's not unheard of. If things look very dire, think about switching country. I know someone from Germany who rescued her thesis that way. The way she explained it, things went very bad with her previous adviser and she would not have been able to defend at her university or to switch advisers. But a professor at my university thought the work was good and took over the thesis almost at the end, asking for about 6 months of work to correct and add various things.
Start over. It might be somewhat more difficult to get hired (or not) but it's not the case that it would be impossible to get funded Europe-wide. Here again, if some country-specific regulation regarding grants complicates things, consider going to another country. As noted by Pete, going back to the US is also an option and would be easier to explain later on.
You can also seek advice from other people at your university. There might be a research coordinator, a PhD “coach” or councilor or some HR person whose role is to help in those situations. But whatever you do, be very careful how you present things: “my adviser is incompetent” might not go well.