I completely agree with you! I think all those anime you mentioned above are very overrated! Most of them either have useless filler, or are just not as amazing as you would believe they would be with everyone freaking out about it. One that is REALLY over rated is death note. Everyone kept telling me to watch it so one day I watched the first episode and was quite disappointed. I didn't quite understand the appeal of it at all!!
Air was honestly my favourite key anime of all time. Don't get me wrong, I loved Clannad, Kanon and all the others but I felt that air had the best character development and story.