Is the flight simulator logable?

Yes, the flight simulator is classified as an AATD, and is logable.  Credit towards a FAA rating is limited as outlined below.
2.5 Hrs for Private Pilot Rating
20 Hrs for Instrument Rating
50 Hrs for Commercial Pilot Rating

Do I need a CFII present to log the time in a flight simulator?

Yes, except for one condition.  If you hold an instrument rating and are within 12 months of your last 6 approaches (or IPC), then you can use the flight simulator solo to gain your instrument experience (i.e.  6 approaches, holds and VOR tracking) per FAR 61.57(c).