I agree with Yellow on this one. If I were to rank them, this is how I'd rank 'em: Thermal grease and pressure > thermal paste > thermal tape > that white goop that they use at kd/dx
The tape is an adhesive, but not quite what you would be thinking when you think tape. Think of a gummy sheet of tacky gel with bits of diamond and ceramic dust embedded in it. Comes on a clear plastic backing. Comes in different thicknesses, great for its reworkability, but lacking in performance. the 3m stuff I got is better than the white gunk it replaced, but I would still pick thermal grease and mechanical pressure to any adhesives.