The problem with rating these games is that they are all reflective of wildly differing DM styles, or at least that's my impression from playing Icewind Dale, Planescape Torment, Baldur's Gate and the part of Baldur's Gate 2 I have managed to get through. Icewind Dale's DM is one who is running his campaign out of the most rigid pre-published module to the letter, with the story never once attempting to engage any of the PCs individually in the story by giving them any stakes or advancement of their character arcs and instead existing purely to be in service of providing dungeon after dungeon to pillage in much the same way that the plot of a porn film only has a plot to string together sequences of shagging.
Baldur's Gate was certainly better in getting away from the overly linear structure of the world and attempting to develop a character arc for the player's PC and trying to provide character for each party member, but the plot took too long to provide the main character with any sense of investment, individual party members promptly turned into virtual blank slates once they joined the party, and too much of the earlier portions of the game seemed dedicated to making the characters wander aimlessly to looking for gear (as opposed to following up on rumors) and delving into dungeons that had nothing to do with the plot in order to find equipment to give them halfway decent odds at survival; furthermore, while complete and total linearity in IWD was annoying, BG was so open ended that it was in danger of passing the poing where it started to harm the narrative structure (a problem that plagues some of the early Ultima games).
BG 2 seemed to improve on the non-characters in BG, but its strategy for doing so thus far is to constantly have the PCs dump lines of text at the slightest provocation at the most inappropriate times, with party members engaging in ham-fisted melodrama during what should be a tense and exciting jailbreak sequence; maybe this isn't the case for the rest of the game, but my initial impression of the storytelling is not exactly favorable.
Planescape Torment is the kind of PnP game I have always wanted to be in and am currently in the process of planning, where role-playing is the main focus and combat comes into play only where appropriate to serve the story as opposed to coming up with contrived reasons for monsters to fight the party every other five minutes or having the combat exist solely as a means to acquire more magic gear to improve at combat (and on and on in a perverse cycle of circularity akin to why a WoW player raids
), the story both rises above the tropes that plague standard fantasy (an oxymoron if ever there was one) transcends above mere genre storytelling to tell a meaningful tale that touches on fundamental issues of philosophy and storytelling. Most importantly, when combat comes up, the story never once feels foisted into the player via unskippable dialogue with party members and exposition in the middle of what should be an action scene, with exposition feeling entirely natural and largely optional.
tl;dr: PT>BG2 (first impression)>BG>IWD, because I like playing with DMs who make a roleplaying game focus on roleplaying and narrative.