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 (see below) per FAR 61.57(c).

61.57 (c)…

(3) Use of an aviation training device for maintaining instrument experience. Within the 2 calendar months preceding the month of the flight, that person performed and logged at least the following tasks, iterations, and time in an aviation training device and has performed the following—

(i) Three hours of instrument experience.

(ii) Holding procedures and tasks.

(iii) Six instrument approaches.

(iv) Two unusual attitude recoveries while in a descending, Vne airspeed condition and two unusual attitude recoveries while in an ascending, stall speed condition.

(v) Interception and tracking courses through the use of navigational electronic systems.