Hi Rose,
TG2 can compute *much* more detail than the TG classic ever could. More things to compute take more time, it's not entirely a question whether other things are running in the background.
Most importantly, there's a sticky thread in the discussion forums called "render settings recommendations", which is absolutely a "must-read".
In TG2, it is very easy to use render settings that are way beyond what is required for your scene, and this article is going to help you understand how to make clever choices about your render settings.
I daresay that if one would create a scene that only has the same elements that TG classic was able to use (heightfield, surface coloring and 2D clouds, no GI, and a render quality setting of 0.5), you will probably find that TG2 is actually faster, especially because it is multi-threaded.
Regards,
Frank