As I'm currently very much into visual novels, I've been wondering for some time where to draw the line between game and not game.

I don't think there's any question that Ace Attorney qualifies as a video game. It actually has gameplay, what with the investigations and cross-examinations and giving you a Game Over if you fail too many times.

Little Busters!, too, I would consider a video game. While it doesn't have the puzzles or investigations of Ace Attorney, it does have minigames and your choices have a big influence on where the story goes, with the "Bad Ends" being more or less Game Overs.

Then you have visual novels like Higurashi: When They Cry which have little to no interactivity whatsoever. Higurashi has exactly two choices, and neither have any influence on anything beyond the next few lines of text. There's also the TIPS which are basically little extra chapters you can read whenever you want, but that hardly counts as interactivity.

And then there's Planetarian which has no choices of any kind and is just a linear story from start to finish. This is really the point where the only interactivity is pressing a button to advance the text, and nothing more. It's still different from reading a book, as it's supplemented by graphics, music and voice acting, but does that make it a "game"? Hardly.

I still consider all of them games because the line between when it is a game and when it's not is a bit arbitrary. To me, Ace Attorney and Planetarian, even being the two polar opposite extreme cases, are still fundamentally representatives of the same genre. And if I consider Ace Attorney a game, I feel like I should consider Planetarian a game as well.