Preview is a markup tool, not an image editing tool.
On OS X it is either Acorn (my preferred tool, because you can cut/paste excel spreadsheets into it elegantly), or Pixelmator (which I also use occasionally)
Depends on what you mean by 'editing'. I can crop, resize, rotate and stitch together images in Preview which is editing in my book and covers about 95% of all image editing I ever need.
On OS X it is either Acorn (my preferred tool, because you can cut/paste excel spreadsheets into it elegantly), or Pixelmator (which I also use occasionally)