Well, PTDE will get delisted after a while and this will be the only way to play Dark Souls 1 in the future. But yes, online PvP will be more active in the remaster, so if you like PvP then you will enjoy it.
As for the graphics improvement, it is not confirmed that the graphics will be the same after launch. Most of the preview builds are not final build. Only after release we will know if there are any graphics improvement.
Edit: Plus, they are adding a lot more improvements, such as easier way to switch covenants without having to trek hundreds of kilometers to do this. Also, like DS3, long holding the up or down buttons will select the first item in the items list. Also, resizable UI.