If you liked the Flag anime, the Anime-Planet community thinks you'd like:
Two major world powers have constructed the most dangerous weapon on earth: Tactical Armor (TA), an elite fighting mecha with extreme agility and fighting strength. Yushiro Gowa is the top TA pilot and captain of the Japanese Self-Defense Force, an orginization that uses the TAs to try and bring honor back to Japan. Yushiro must make a hard decision and face the truth about his past and the secrets of the Gowa family, who will use their adapted spiritual powers to summon Gasaraki and unleash terror on all of mankind.
Although their plots differ significantly, one of the strengths of both Gasaraki and Flag is the melding of the mecha genre with a sense of "real world" politics and military structure. Both series take place in a near-future where mecha are a new and game-changing addition to the military landscape, and they tend to be shown as fallible and experimental pieces of equipment, rather than the omnipotent, gravity-defying super-weapon. If that "real world"-feel appealed to you in one of these series, you will probably enjoy that aspect in the other.
One word... Realism. These two anime are both very realistic in their approach to the subject; third world nations at war and those involved. Although there is a decent amount of metal action for Mecha fans, its not over the top, Gundam style, and not too little that it leaves you dissapointed. i enjoyed both shows very much.
Beppu Yugo is one of the world's most successful and celebrated negotiators. His cases have ranged from big to small, from secretive to in the public eye. His work doesn't come cheap, but his skills are the top of the line, and through words, not violence, his failure rate is minimal. After a period of inactivity, Yugo is back on the job, to help negotiate the release of a hostage in Pakistan. With harsh terrain and deadly enemies before him, will he survive long enough to save the hostage, and return with his life?
Yugo and Flag are both remarkably similar: they have a slow pace and similar animation, but most importantly they are each focused with terrorist-laden third world countries and have a very realistic sense of the military. I enjoyed Yugo a lot more than Flag, but there is an unmistakable realistic quality to both (except for the robotic weapon in Flag, that is). If you liked one, I'm thinking you'd like the other.
Perhaps I should not make this recommendation, since I like neither Flag nor Yugo the Negotiator. Nevertheless, consider this a negative review of why you might like one of these, if you enjoyed the other.
Both anime are pretentious -- meaning, they obviously think very highly of themselves in terms of psychological insight and political analysis. In my opinion, both are entirely superficial, and have no real depth to their depictions. The psychology presented is pop psychology, and the political analysis is simplistic and slanted.
It has to be said, though, that if you found yourself thrilling to the courageous achievements of Yugo, you'll surely be captivated by the way that Flag slowly entwines you in its story.
So don't let my negativity dissuade you -- if you genuinely liked one of these, give the other one a chance.