Hey there! First want to say that I love these! You've done a great job making some puzzle games that don't feel derivative, and that's no small feat!
I've played Pairs and Gravity quite a bit, and in general, really enjoy the gameplay in both of them, but I think they both suffer from the same problem: they are too easy. Does the difficulty change at all as you progress in either game? I could imagine introducing more block types to make it more difficult, or introducing more blocks sooner as the score progresses.
I have another feature request (that is actually related): session saving. I went back to the home screen from my first play of Gravity with a score in the thousands (but nowhere near ending the game), and was disappointed that the game didn't save my progress.
I think it's worth asking yourself what the target gameplay length is for a session. If you want the user to be able to play indefinitely, that's probably okay, but then you need to save the game when they exit, I think. But my preference is to aim for shorter play, so the user can feel a sense of mastery as they get better and have higher and higher scores.