Well, if you strap the input to any ADC down to 0v, you get a count of zero... so... it looks like your software configuration of the PIC or the ADC is shot...

1. Make sure your PIC pins are configured for INPUT (TRIS)
2. Make sure your PIC pins are configured for ADC
3. Make sure Comparators (if they share the same pins) are Switched OFF
4. Make sure you have configured VRef+ and VRef-
5. Make sure that if you have set VRef to EXTERNAL you've connected something to them
6. Make sure your sampling time is sufficient for capture
7. Make sure your justification is correct for 8 or 10 Bit mode

If it's similarly happening on multiple channels, then the chances are your PIC pin is good.

If you have a scope, the ADC should faithfully follow what it sees on the PICs pin. I say that, because the first and last 20 degrees of travel on many a junk POT doesn't do much as the wiper travels over the end stop.