We're planning a family trip to Greek Islands in June. But we're confused with that which island would worth to visit and which wouldn't? Because we're not going to visit all of them. Please tell me the best ones.

'Best' depends on what you decide it is and will be different for everyone! Some general guidelines (or sterotypes ha):

Santorini for romance
Mykonos for partying

We stayed on Naxos for a week with my family (2 60 year old, 3 30 year olds, 1 40 year old) in Sept last year and loved it - cant wait to go back.

Rhodes, Crete, Paros Corfu are all popular.

I think you need to do some research with guide books or on the internet and decide what your priorities are, whether you want to fly to the Islands or take a ferry, look at ferry connects, decide how many islands you want to visit etc. Once you have an idea of what is available we can help you out more. As it is your question is way too broad!

Happy travels!

I think all the islands are worth a visit (!), so you really have to narrow the question for us! What are the ages of your family and what is your budget? What are your interests and how much time do you have? Thanks!

Seeing another post of you, where you seem to have an excellent knowledge of Turkey, i assume that you live there ?
If yes, you could easily visit the nearby islands, such as Lesbos, Chios,Samos, Kos ,Halki or Rhodes.

Yes, I live in Turkey. But i don't have enough time to visit all of the islands this summer. I only want to know that which islands do you recommend firstly. 3 Adults (one 24-year old) and one 15-year old.

I think even if you wanted, it wouldn't be possible to visit all Greek Islands....
In order to receive the right answers from the forum, please let us know a little bit more about your interests and expectations.
Not all the islands are the same, plus as i suggested, depending on where you live in Turkey, you could start with neighbouring islands

You really need to give us more to go on, otherwise you will get responses like this:

I recommend Naxos (because thats the only island I have been to).

I understand what you're all saying We have been to Kos, Athens, Salonika and Kavala earlier so we want to visit a much more different place. I like sightseeing, nightlife...etc isn't important because it will be a family trip, we like visiting villages, we want somewhere where we can also swim...etc but the most important thing is that I'm asking about the more popular ones such as Rhodes, Crete, Santorini, Mykonos...

Well in that case I would recommend Naxos...for real Its big enough to offer lots of little villages you can visit by renting a car, has loads of lovely beaches and great places to eat. The harbour is lovely and you can also do day trips to Santorini, Mykonos/Delos if the weather cooperates and you are so inclined!

Crete could keep you busy with sightseeing for weeks! It has lovely beaches and smaller villages, as well as some larger cities with airports which make for convenient travel. Knossos and Phaistos are two very interesting Minoan sites, however they are quite well known and very crowded. Central Crete has several other smaller Minoan sites that you would likely have fewer crowds.