Which is best Gamo or Crosman air rifles?

Both companies make fine air rifles. Your question is too general. It's like asking which is better Honda or Toyota without comparing two specific models. Crosman is a larger company and makes air rifles in all categories from inexpensive to costly. Gamo is a smaller company and makes air rifles in the medium to costly range. So trying to say one is better than the other is not a fair comparison. They both make fine air rifles.

Now if you had two specific models then you could make a comparison.