Torchlight isn't bad; Diablo-style mowing through enemies, some very simple quests, etc. Nothing spectacular but considering the price quite good.
Gratuitous Space Battles is fun to play occasionally but holds little long-term motivation (at least, it didn't for me). Steep learning curve but very flat once you mastered the basics.
Fleet construction is fun in the beginning but becomes unwieldy and tiresome as more and more components are unlocked.
The battles itself can be fun or arduous, depending on how well you set up your fleet and on enemy fleet make-up.
They are nice to watch but sooner or later, they offer little new.
S.P.A.Z. (Space Pirates And Zombies), I played the demo (first two systems only); quite fun but very soon becoming repetitive. The 'diplomacy' system is rather 'meh' (two sides in each system, gaining favor with one reduces the relationship with the other - and despite being the same two sides in each and every system, the relationships are per system only).
Fights range from frantic to boring, depending on the weapons used.
High grind factor and rather bland 'side quests'.
Considering that you can get these three games for very little money, they are quite good, despite their shortcomings.