Just like renting your house you can rent the RV and make a profit.
In that sense RV is an asset that can produce an income stream.
That is my definition of an investment.
Of course if you use it for personal use only it is just an expense and liability.
So unless you are going into the rental business I would stay away from the word 'investment'.
Home or RV I see them as the same. Home probably holds its value better and has the advantage of the land that tends to appreciate where as the RV has no land.
Some homes have done very poorly.