I have several thousand slides and color negatives from a lifetime of 35mm photography that I have been wading through. (Wish I had cataloged them at the time).
My approach was to buy (check eBay - anywhere from $20-$50) an inexpensive 35mm slide copier (these usually come with instructions on how to get accurate focus) that screws onto the lens of my digital camera (Nikon Coolpix 990 3.3mp) and either point the camera at the sky in daytime or a white card lit by a photoflood lamp in the evening. I have not tried flash, although that should work OK.
You now have a JPG of the slide/neg that is much better than anything a scanner will produce.
I use Photoshop to convert neg to pos but other software described previously may be able to do a satisfactory convert.
Any real gems you find can be printed from the negative.
I think I once read that to get the equivalent of a 35mm negative, you'd need a 25 megapixel digital camera. Anyone have the correct equivalent?