The poems in A Shropshire Lad are nice because you don't need a Masters in Poetry Appreciation to enjoy them. That's why I read them in high school, and that's why they've stuck with me since then. Dragoon's assessment is realistic; if I knew more than two or three poets I would be able to offer an opinion as to whether some poems in it are truly great. In my opinion, the ones that are really, really good are:
With rue my heart is laden (short, simple, powerful, perfect meter, elegant)
Terence, this is stupid stuff (wise, humorous),
Others, I am not the first (just plain stylish)
I read through A Shropshire Lad every so often, just because every time I do, some new poem catches my eye and fancy. Just to highlight the ones I have a fondness for, here they are:
XXI   XVII   XLIX   LI   LVII
Anyway, the main reason for this write-up is that I have noded all the remaining poems in the book, so go take a browse.