The first two titles in the Eye of the Beholder are classics and the third isn't too shabby. Have your graph paper at the ready as you descend into the labrynth beneth the bustling city of Waterdeep. Your harty party of adventurers will need to use thier wits and more to stay alive. Cut off from the world above your only hope is to push onward to danger and victory! Seriously though these are classics in every sense of the word. Taking the best parts of Might and Magic and the Bard's Tale along with the Dungeons and Dragons ruleset and the world of the Forgotten Realms, PC dungeon exploring doesn't get better than this. Once you've finished all three games pick up Archive Col. 3 and start up dungeon hack which uses the same game engine for infinite adventure.
The Gold Box series is the stuff of PC roleplaying legend, and to get it all for $9.99?! You can't go wrong. I recently found my archive CD from the mid 90's but of course I was missing the hint books. The fact that it all comes in one giant package for one low price is a blessing not even the highest level cleric could bestow. Buy this now, but one word of warning; once you get sucked in it will be a long while before you get out.