I cannot say enough good things about Murder in Baldur's Gate. I've run every Encounters module since season 4, and MiBG was hand's down the most fun for my players. Plus, I think it really sets things up for an epic campaign to take place. Plus, the way it's written is extremely open-ended so you can pad it out or tighten it up to suit your group.
Against the Cult of Chaos is also pretty good. It's got slightly railroady sections, but players can choose which facet of the mystery to investigate. Plus, it has nostalgia references galore, being a mashup of Keep on the Borderland, Village of Hommlet, and Against the Cult of the Reptile God.
Similarly, Legacy of the Crystal Shard is pretty good. It's designed so that players will have to choose what to fail at, something you rarely see in modules -- there's literally too much going on for the group to be everywhere they need to be at the right time. The scenes for the boss fights are classically picturesque. I also thought the villains were nicely fleshed-out, similar to MiBG. There's several tie-ins if any of your players are fans of R. A. Salvatore; not having read any of the novels did not hamper me as DM.