Having done no other martial art for close to 20 years, my vote is that aikido is a terrific first, last, and only martial art!
Nothing against doing multiple arts, but why the need? I have learned committed attacks through aikido. I don't think my aikido has suffered due to lack of some other art. This is a question that each individual answers for themselves, and cannot be answered universally in this type of forum; but for me, the answer is an overwhelming yes.