Good post IJonTichy. This is a forum topic that deserves to crop up every now and again.
First of all I would say that I really like Matrix and HPS. They offer some great gaming alternatives to the mainstream PC gaming companies which have been decidedly lackluster these past 6-7 years. Still, however, as some people have mentioned in this forum, with a few notable exceptions Matrix tends to market games on the more well-known and sometimes overdone campaigns and battles.
Anyway, my two cents:
The Campaigns of the latter Roman Empire - As with films and literature, the Roman games seem to concentrate on the the Republic rather than the Empire. I'd love to see some campaigns like Marcus Aurelius' Macromanic Wars, the Crises of the Third Century (Zenobia, Aurelian, the early Goths), Julian's campaigns in Gaul and Persia, and Attila's invasion of the West. These would be ideal for playing on a strategic map then breaking down to tactical battles. Although Rome: Barbarian Invasions did a reasonably good job with it, it has some notable flaws like one basic time period with no period scenarios. Also, it seems with Rome: BI, once the Western Empire gets past the early financial, political, and military crises, it plays out much like the first Rome: Total War game did where you have to capture a set number of provinces before the clock runs out.
Manstein's backhand blow (1943) - Would love to see an operational game on this, Germany's last serious victory of any consequence. I think this third battle of Kharkov was more interesting than the overdone second (1942).
The Solomons Campaign (1942-43)- Although this was done very well in Uncommon Valor, I think there is room for others to try their hand at it. After all, it was the greatest land/sea/air campaign of all time, with the US and Japan more or less at parity.
The Hundred Years War - There were a lot of interesting campaigns in this war, notably the ones with Edward III, Henry V, John of Gaunt, and Joan of Arc. Like the Roman campaigns, this would be a good one for playing on a strategic map then breaking down to a tactical map for the occasional battle.
The Russo-Japanese War (1904-05) - One or two of you have mentioned this one. It was a fascinating land/sea campaign that could have turned out much differently than it did had the Czarist forces had better strategic leadership, and had the Japanese had been a little less lucky.
For World War One, would love to see operational level games on the Brusilov Offensive and Germany's 1918 (Operation 'Michael') offensive. These campaigns were rather fluid and much more interesting than the usual trench warfare and meat grinder battles like Verdun and the Somme.
A strategic Starcraft game - I know some of you wargaming purists are going to wince it this, but I always thought that the Starcraft universe would lend itself very well to a big-scale strategic treatment. Also, I don't know about the rest of you, but I've not been crazy about the grand strategic science fiction games on the market (Galactic Civilizations, Space Empires, Master of Orion, etc).
In closing, I would add that I was delighted to see John Tiller do the Dien Bien Phu game, what with the French-Indochina War being almost totally ignored in the gaming world until now. Although there was an Operation Art of War scenario on the battle of DBP, it was terrible in that the AI was totally incompetent as the Viet Minh.
Cheers, and prog rock on!