Which hotel provides the best quality base/ordinary room for the fountain in the strip?

Do you mean the Bellagio Fountain Show? Outside of the Bellagio itself, you can view the fountain display/show from the Paris Las Vegas Hotel & Casino, Planet Hollywood Resort & Casino, Jet Luxury at The Vdara, and the Vdara Hotel & Spa at ARIA Las Vegas. I am not sure which offers the best pricing currently, you would have to check into it.

I have only stayed at the Vdara Hotel & Spa at ARIA which to me, would give you the best view without actually staying at the Bellagio but this depends on your room. You can see virtual tours online for a lot of places these days, might be worth checking out before you book anything. 

I stayed at Planet Hollywood once and had a good viewing of the fountain show. I was somewhat surprised as well because the room I was staying in was not all that expensive!  

I would say the Bellagio, but I have yet to stay there. I imagine their rooms are a bit more glamorous than ordinary, but I would still want to go. I think they would also have the best view of the fountain. 

Bellagio would give you the best view of the Bellagio fountains but there also rooms at Paris in which you can see the fountain show.