*Stands upon a high rock and points outward in a heroic pose* GENTLEMEN! THAR BE THE FIERCE OLDBIES MARCHIN' THISA WAY!
Seriously, I'm half in half, on one hand, it depends, if you mean 'Re-make' you mean update the graphics? Sure why not, all it's hurting is peoples nostalgia goggles. If you mean rewriting and altering the plots, settlements, or anything in between? No, don't fix what isn't broken.
(However, I wouldn't mind being able to see Vault City in 3-D)
I wouldn't be against it if all they did was make it in 3D and give everyone a voice actor.
But how likely is it that that's all they'll do?
They'll likely change perks, skills, SPECIAL, characters, dialogue, mature content, factions, wasteland, cities, groups, creatures, items, interface, HUD et cetera.
So that's why I'm against it.
If they could do a complete replica only with better graphics and voice actors for everyone and have better Talking Heads than FO3/NV/Obl had then I see no problem with it.
But it's very very unlikely they'll just do that if they remake them.