I disagree with one of your fundamental assumptions here. Yes, a game is something you "play"; but that doesn't mean that everything you "play" is therefore a game. My view (to steal some lines from posts I've made in other threads) is that the english language uses "play" to describe two distinct kinds of activity.
The second is playing like a child plays with toys. The activity here is exploring possibilities through interaction. The psychological drive is curiosity, which I'd describe as wanting to see everything there is to see. When you search obsessively for all 100 Green Stars because you've heard that unlocks a secret ending, curiosity is what's motivating you.
(Of course, this isn't to say that every case of 'play' has to be only one of these two types. Human beings rarely have only one motivation to be doing something.)
"Interactive virtual experiences" can be games, but they don't have to be. A "videogame", by definition, has game elements and thus provides a challenge. If you go around urging people to consider how "videogames" don't need to be "games", you really shouldn't be surprised when people take you to task for trying to redefine a term.
I am not surprised at all, there is a whole world of people who assume that someone has agreed on the definition of 'game'. I myself was claiming things not to be games and rather 'interactive experiences', to great annoyance of my teachers a few years ago. A definition proposed by Callois in 1961 has no meaning although apparently this unsigned agreement about 'game' is.
I am not saying that a video game need not be a game. I am saying that a game need not be competitive, nor have challenge as its highest goal. This is not a new thought, again. The definition of 'game' is like the definition of 'play' very much in flux, true. But don't assume that because many people say so 'game' must mean 'something which has among other properties challenge'. Many people will attest that a game can have a high level of 'immersion' whereas immersion is more properly an attribute gained from the
apparatus being of 'imposing' (if you will) value. Many people use 'immersion' to mean what is commonly meant, but that does not mean by mob rule that this is what the word means. This is the case I make for games having to 'include challenge'; I think that is a common misconception derived from a large focus on the competitive factors of games.
I myself prefer to follow Callois' indication and keep the term 'game' open. I cannot stand modern writers who suddenly say games must have a quantifiable outcome, games must have a set duration... The term 'game' can be used far wider without excommunicating many forms of game without offering them somewhere to go but 'experience', which is a thorough useless nondescript term. One may as well say that a film needs to have a narrative and without narrative it is 'moving pictures'.
Games
may include a quantifiable outcome.
Two children playing at being jungle explorers are playing the game of being jungle explorers, not playing 'the toy' of jungle explorers, nor playing 'the experience' of jungle explorers. They are pretending to be jungle explorers and this mimicry defines the rules of the game. You could say that if one uses common sense he breaks the 'game' and 'looses' but that is more of a magic circle-related element and not game-specific.