I'm a collector, certainly, but it would be more accurate to say I dabble in collections.
I daresay (oh yes, I dare to say; sometimes I even dare to daresay) none would be worthy of being called a real collection by truly serious hardcore collectors, but I nevertheless have a few individual items that are without doubt rare and desirable.
Certainly in my few thousand records there are some nice treasures, but it's a selection tailored to my own personal tastes and not any sort of "completion" in any segment. This is probably like what DR Rodzinski is saying about his, with probably three times what I have. CDs round out some areas of this, of course.
Blu-rays, DVDs, and a few remaining laserdiscs are a collection, but the same disclaimer applies.
Other smaller collections are certain books; musical scores; a handful of film posters; a few types of maps; some vintage cameras and souvenir collectors plates and such, representing mid-century road travel; and no doubt a few other things that don't come to mind at the moment.