This will be Bush's legacy, and it should be. It is his greatest accomplishment (so far).
If W had secured the borders early in his second term, (instead of wasting his efforts on trying to tame the Social Security monster), he would have probably been able to get much of what he wanted in his amnesty bill. That fiasco, and his failure to lead his party in support of the war, will overshadow his accomplishments for a long time.
History, however, will be kind to him.