papillon wrote:
I say play because of the restrictions the medium places on the experience and the state of mind that puts me in. I can't read a VN like I'd read a book or a bit of web fiction, I can't control my progress through the story as easily, flip back and forth between favorite bits, etc. I'm progressing through a designed experience. The fact that I am reading most of the time is secondary.
Most video games include at least a little bit of reading. Watching fansubbed anime includes reading, but most people would still say they're watching it rather than reading it, even though they're clearly doing both. I'm reading the text that I'm typing right now, but reading isn't the primary activity I'm engaged in.

That lack of control makes me feel like I'm reading rather than playing though. Most visual novels let me make decisions that determine how the story progress, but I can't control how the character is going to do something. Like in Fate/Stay Night, I couldn't control how Shiro fought in the combat scenes. The VN held my hand and told me he did this, this, and this.
There are some games, like Heavy Rain and Fahrenheit, that feel more like interactive movies, but usually games give you the ability to control what and how you want to do things. Every gamer is different, but I personally would feel frustrated when playing an rpg game if I was told what equipment to use, what skills to level up, and how I am going to fight a boss. I don't want to be Llair, the reckless warrior who hacks and slashes his way to victory. I want to be Llair, the resourceful fighter who does unconventional things that may or may not work.
I probably said too much, and I apologize. >_<
As a summary, I feel the main difference is that even though VNs have interactive elements, I'm being told a story, and when I'm playing a game, I'm actually making my own story and experience.