This was easily the most polished and refined game of the series so far. The story was presented well and video clips didn't draw on too long (like part 1) and the gameplay was varied enough to warrant the number of levels (unlike part 2 which was a little samey at times). There were still some flaws and room for improvement however.
Here's a break down:
Level design
The design was very good. The levels flowed well and were full of imaginative rooms and little graphical touches that made the game stand out for me. It may not be the most graphically polished game on the forum, but for me, it certainly wins the prize for the most interesting. You've really made this series your own and you can have pride in the fact that there are no other games like it on the forum (and if there were, they'd be sub-par copies). I particularily liked the first section of the conservitory level. It really reminded me of Bioshock. I'm not sure if you took any inspiration from it, but regardless, it was very well done. Some more climbing puzzles would have been nice. These were the funnest part of the game for me. I know the gas level was pretty much devoted to climbing, but I would have liked to have been outside the station longer, climbing across balconies and scaffolds etc.
Audio
The audio was better balanced than in the last two games but was the biggest flaw with this one. While voice overs were loud, the music was so quiet that at times there was hardly any point of it being there. The final level, while great in it's own right, could have been made all the more awesome if the music had been increased in volume. But as it was, it was a little piddely background nose. The ambient "background" noise was far too loud and was more obtrusive than the music would have been at that same volume. For the last part (and you MUST make a final part) you need to consider doing a beta test to sort this kind of stuff out. I offered to fix some of your audio balance out a while ago, but oh well, that's the way it goes. Voice acting wasn't too bad, if a little corny at times and over/under acted. But it fitted nicely with the scenario. The princess was the most entertaining. She seemed to forget her lines halfway through her speech. xD
Gameplay
Gameplay was nicely varied. There was still room for some more elements but ultimately the levels played well and were all entertaining, except the church level which I found pretty dull - There was nothing massively inspiring in the level design and there weren't many enemies to fight either. Kudos to you for the last level though. It was really excellent. My only gripe was that the ending was a little odd. I entered the last room, got a video of the prince being shot, then shot him myself and then the game ended. I think the video should have played when the prince was killed. It would have made more sense and been a better ending. There weren't many bugs in the game. I got a few invisible barriers that I had to navigate, but nothing terrible. There were a couple of things like the revolver constantly playing a few frames of animation, but ultimately, it was a nicely polished experience.
Presentation
The loading screens and menu were much better looking than previous games. The credit sequence was a nice touch (although perhaps a little long-winded when it extended into level 2). A few grammatical errors here and there definitely didn't spoil the experience for me but just remember that there are plently of people on the forum who'd be happy to proof read your projects to catch anything you've missed.
Ultimately, I really loved the game. I hope you consider a final part. You've come too far with this series to give up now. Just know that, if you do decide to make the final part, I will already be signed up (if you'll have me). Just drop me an email.
If this game doesn't get you a BOTB then you are very close to one.
Congratulations on completion.
