The terms you have used in your question are more colloquial than precise or definitive, so comparing against them is not necessarily useful. Technically you're comparing different types of 'projection', plus the viewpoint that the projection is done onto.
Final Fantasy 6 uses an orthographic projection, though a very specific one that is perhaps easiest described as a degenerate oblique projection where the receding surfaces are drawn at a 0° angle rather than a more illustrative 30° or 45° (as in Ultima VII). The viewpoint is typically from above and offset somewhat from the area being viewed.
GTA1 uses a fairly standard orthographic projection. The viewpoint is directly above the subject.
First person games use perspective projection. This projection is also used for most third person games rendered in 3D. In 1st person games the viewpoint is placed at roughly head height on a notional person, but in 3rd person games the viewpoint might be placed behind a person's shoulder, or high above the world, or in any arbitrary position.
Isometric games are, of course, in an isometric projection. However, Fallout 1 and 2 are not technically isometric - they are trimetric projections. You can see the difference in how Fallout is slightly rotated compared to a typical isometric game. For a game to be isometric, the angles between the 3 axes need to be equal, ie. 120°. Examples are Final Fantasy Tactics and Sim City 2000. The viewpoint is pretty much the same as for the oblique projections.
Oblique, orthographic, and isometric are all types of parallel projection where lines that would appear to converge in real life when viewed in perspective, are rendered as parallel lines instead.