Here are some of my favorites, each with different appeal. I would say that the first volume of "Crossroads" is a good career overview. It was one of the first major boxed sets that proved the viability of the concept in the CD era. It is more varied than the "Live in the 70's" approach taken with "Crossroads Volume 2", which may or may not work for you. I tend to like his better individual albums than Crossroads, but it is a good overview of his career. Here are my top Clapton albums:
1) Derek & The Dominoes- "Layla" One of the great albums of the 70's, and perhaps the finest example of an overtly guitaristic approach, which has not always been the route that Clapton has taken, particularly in studio albums. This is passionate and energetic music, aided immeasureably by the contribution and inspiration of the great Duane Allman.
2) "461 Ocean Boulevard"- This very relaxed album will not appeal to everyone, but it is a virtual template for much of his more laid back material, including the immensely popular
"Unplugged". 461 is a very pretty and delicate record which I have always loved. It really introduced him as a singer, something he has not always been given credit for, but clearly one reason he is so popular. It has a few hits, but mostly nice quiet, subtle songs such as "Better Make It Through Today", "Let It Grow" and others. Nice late night music.
3) "Money and Cigarettes" This album is probably not entirely successful, but I like the interplay with the american band, including the great Ry Cooder and Duck Dunn. Strong and rocking songs, with nice studio sound.
4) "Twenty Four Nights" This live album, taken from a marathon run at the Royal Albert Hall captures a nice overview of his main styles, and I love the symphonic version of "Bell Bottom Blues". There is also a DVD of this for the video users amoung us.
Happy hunting...