IWD vanilla is the best - it has great pacing, best atmosphere and itemization. Also the dungeons are unmatched by any other Infinity Engine game. It is the pure, real Icewind Dale experience before all the "balancing" took place. Also, talking to the locals <NPCs> is more fun than in Baldur's Gate. The NPCs are colorful and offer some roleplaying opportunities, more than in Baldurs Gate.
Heart of Winter - I like it, but wish it would not retroactively change the vanilla game. The expansion addas new spells and these are nice, but here is what I especially do not like: new itemization which removes some items from the base game and new paperdoll graphics (ew). It also adds a sneak attack which I enabled for 5 minutes to check it out - prefer backstabbing by a mile. Aside from that Lonelywood is a great town, the overall mood is great (BARBARIANS!), dungeons are a bit worse, but still great and look nice. The campaign also does not overstay it's welcome, which was considered a minus by reviewers at the time, but I like the length of HoW.
I also prefer to play HoW after finishing the base game, so the story flows better and the sequel implies that order.
Trials of the Luremaster - never played it.
IWD2 - never finished it, played it up to the middle of the game (I think), it was nice, new ruleset was good and interesting, but the mood and pacing was way worse that the original IWD or its expansion. Music is great but after it cuts out it does not come back - it ain't looped? The combat was better, but encounter design not necessarily - I felt like sometimes there was too much fighting, a feeling I did not get when playing the original game. IWD1 broke fights more often with settlements and/or NPCs. I think it is still better than BG2:ToB which I never finished, even though it is shorter than IWD2.
I am not sure but IWD2 feels to be longer than IWD+HoW, so I would recommend the vanilla game.
IWD:EE: If you play it the Pope himself will damn you and make sure you go to hell. EE rapes the original game by introducing new bugs, old bugs (which Rimhog never fixed as far as I know), introduces new spells and classes from BG2 which unbalances the game immensely - playing as any of the new classes is pretty much cheating.
If you want to play the original game download Microsoft Compatibility Toolkit>Install>Run Compatibility Admin. 32bit>Righ Click New Database>Create New>Application Fix>Point to IWDmain.exe skip compatibility modes (click next) and check the following fix: ForceDirectDrawEmulation. Save and Right Click the database to Install. Now you have the vanilla game running on win7 and saved some bucks for hookers and booze.