A few short bullet points:
- Nikon no longer makes film scanners, though some are available for sale as new-old-stock (NOS)
- Best is hard to define. High end reprographic shops use both drum and flat bed scanners for commercial work. Both are large enough to fill your kitchen. The current general benchmark for quality at a high price is the Hasselblad Flextight X5.
- Best value for personal use depends on your needs. Consumer flatbed scanners max out at about ~2400 dpi real-world resolution. This is true regardless of manufacturers claim. This is adequate for 35mm at moderate enlargements and quite good for medium and large format negatives for all but the largest prints. Dedicated negative scanners are a better option for 35mm, though none of the currently-available product matches what was formerly offered by Nikon, Minolta, and others before they all left the scanner business.
My advice would be to do your research. Here is a good place to start:
Detailed test reports and experience reports about film scanners slide scanners: market overview, application in practice
Steve