Yes I'd agree - Candide and Westside Story ae probably his finest achievements. I'm also a great fan of the very early clarinet sonata, the three meditations for cello and orchestra, some of the songs, and to a lesser extent the symphonies.
The symphonies are well made and genuine enough in impulse, but I think there's also an artificiality and almost kitchy self awareness - to be composing such effusively romantic music this late into the century with so many of the gestures of the 19th century, eclectic and modern though they also are, is a bit risky, and Bernstein's balancing of high and low isn't always as insightful as these other guys we mentioned. I think the first is the best and then they tail off in quality.