How to create an image gallery in Drupal 7
It seems like Taxonomy, Colorbox, Views, and the Image field in D7 would be the best way to do it.


Create a taxonomy for gallery
Create a content type for image
Create a View to display the gallery taxonomy
Create a View to display the images in the gallery taxonomy term


I say that is the best approach because it gives you the most flexibility, and will only take you about 30 minutes to set up. Anything else for a gallery (in my experience) tends to be overkill unless you're an actual photo sharing website.