That will depend a lot on your level of interest, the type of photography that you do, and a variety of other things. There are a few for whom a D3s is a suitable first DSLR, and others are overwhelmed by a D40.
Tell us more about your photographic background and the type of photography that you do or want to do.
_____ Brian... a bicoastal Nikonian and Team Member
My gallery is online. Comments and critique welcomed any time!
Welcome to Nikonians! If you plan on shooting in low light, get the D5000. The D5000 has better high ISO performance than the D3000. That said, the D3000 is a very capable body when shooting in decent light or using a tripod in low light situations. For landscapes both bodies are capable of providing excellent IQ (Image Quality). Portraits are usually captured in decent light or with flash, so again either body will work well. Good Luck and Enjoy your Nikons!