I must admit to having a soft spot for the Saint-Saens E-flat major (No.3), especially the fluid, serene introduction to the first movement, but I wouldn't label it one of the best in the set. The D major (No.1) never left much of an impression on me.... and given its relative neglect, I'm apparently not alone in this, which seems a shame. (I probably just need to give it another chance.) As for Alkan's chamber concerti, they're on Hamelin's disc of the Henselt F minor; all the more reason to buy it, I think!
Speaking of concerti in F minor by composers with reputations for writing difficult pieces, after perusing the score thereof, I'm rather curious about the Reger - is Derwinger's recording with the Norrkoping SO under Segerstam any good? (I've heard the Suite in the Old Style, which is also on the disc, and enjoyed it very much, but there are no reviews of the recording on Amazon.)
At risk of going against the spirit of this thread, one of my favourite Mozart concerti is No.11 in F major, K.413 - the orchestral entrances at the end of the exposition and just before the cadenza are, for reasons I can't quite name, two of my favourite Mozart moments. However, it's certainly not one of his most widely performed (especially not compared to its immediate successor, K.414, which I can't stand).