The two questions you presented mean very different things to me.
What do you like to see in a manip?
I like femsub, slower inductions, not much on exhibitionism, milking(?), etc. Essentially just themes in general, and of course I'd like to see said themes in a manip as well.
What makes a good manip?
I should note the following are just the criteria I made up for myself.
- Does the image go well with the text? (ie. Why use
that picture specifically? If someone else slapped another image over your current one would anyone else even be able to tell? If not then your text might be too generic).
- Is the text "well-done"? (Text should be an addition to the image, not the other way around. Which means that if possible there shouldn't be a wall of text. Typos and grammar problems should also be minimal. The font, color, and placement of the text should also help the reader infer who is speaking (if any) and should compliment what you're trying to accomplish).
- And obviously, how good is the actual manip job? =P (Are the edits you made to the image glaring and out of place? Does it look like effort was put in instead of a simple erase of the eye with a spiral under it? Are there too much unused/blank space in the manip? Stuff like that).
Should I base "how good" a manip is upon the number of favorites and/or comments it receives?
While comments and favourites are always appreciated I personally don't give them much weight when it comes to ranking whether a manip is good. They do help slightly in that matter there are way too many variables in both for them to be a good indicator.
(Ex. Nude/more sexual images or popular themes get more favourites overall, comments are more frequent based on an artist's social network, certain themes with a more vocal userbase or are more controversial, etc).