I seem to be one of the few who actually likes The Final Frontier. I remember it getting bagged pretty badly when it came out, people called it Shatner's tribute to himself, all kinds of stuff, but I thought it was fine. Yeah, the special effects were pretty cheapo; Paramount wouldn't fork out for ILM or whoever, so they went with some discount FX company. People thought the campfire scenes were hokey, but I thought they were great. Spock learned to sing "Row, Row, Row Your Boat" by the end. Sybok was cool. A chill, laughing, laid-back Vulcan.
And they weren't trying to rescue God from wherever. I thought it was obvious from the beginning that it was some being a la Charlie X or Trelaine who'd screwed up and managed to get himself trapped somewhere, or was imprisoned, and was using Kirk and The Enterprise to escape. Kirk figured it out right away. "Why does God need a starship?" People said "Yeah, right, they're on a mission to rescue God. How stupid." No. If you thought that that's what they were doing, then I'm pretty sure it wasn't the movie that was stupid.
After the unofficial trilogy of II-III-IV, I thought a self-contained adventure, something like an extended TV episode but on a grander scale, was a nice change. Plus we got character growth, backstory, and some other fun stuff.