Whatever shall I do? George McDonald Frazier is dead, there will be no more!
I feel your pain. May I suggest his Complete McAuslan? It’s his only non-Flashman book that I’ve read and liked. Oh, I’ve read The Reavers, but that was so horrible I refuse to acknowledge its existence (except to warn you in this post to avoid, avoid, avoid it).
I recommend The Pyrates (purely comic novel) and Mr. American (in which Flashman appears as an elderly character).
I read those back when I worked at a library and attempted the Flashman books. I was too young to appreciate the Cowardly Dastardly Bastard as Protagonist. 
As for McAuslan…“God help the German who was stabbed with McAuslan’s bayonet, he would surely die of blood poisoning.” and “I’m not panicking, I’m bloody lost!”
What the hell happened to him after the Missionary’s Wife turned whore drugged him? What happened at the end of Flashman and the Angel of the Lord when that magnificent Black woman let him escape the train? What about the US Civil War, dammit?
Yes, and what monstrous blackmail did President Lincoln hold over him?
Is The General Danced at Dawn worth a read?
Yes, just don’t read it where laughing out loud will annoy other people!
Have you done the Hornblower series?
Have you considered writing the Exhaustive Flashman Companion? A book the world truly needs.
The Sharpe series is sort of a non-humorous Flashman, aka Hornblower on land, aka Aubrey/Maturin also on land.
Which means that it is but a pale imitation of the real thing. No, there is but one Harry Flashman.
Yes and No. 
There is always Fenwick Travers. I almost finished one of them.
Absolutely.
Other worthy reads:
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Black Ajax - Flashman’s dad makes a villanous appearance! Not just for boxing fans, but rather one of (IMO) his better serious works - I liked it better than Mr. American.
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and in particular, Quartered Safe Out Here - the author’s autobiography of his wartime experiences. A truly great wartime memoir in its own right, as well as an invaluable supplement to the McAuslan series.
It is neither pale nor an imitation. They are certainly not the same type of books.
On that we heartily agree. I love Sharpe, but that series just isn’t Flashman. I wouldn’t think that just because someone likes Fraser that they would then like Cornwall. Totally different styles.
Very different styles, certainly, but they’re all the same genre. An as-yet-nameless one, as far as I know, but they’re related.
Imperialist fiction?
Sharpe and Flashman are in British army in the nineteenth century. There is a title Flashman and the Tiger, as well as Sharpe’s Tiger.
That’s about it.
This is getting way off topic, but I would say that there’s an emerging genre of books based on the premise of having a fictional character join the armed forces and fight in (or, in Flashman’s case, at least be present for) a series of historically accurate battles or actions. We follow the main character as he rises through the ranks and gives us a first-person view of all these famous scenes of history. Hornblower was the first that I’m aware of, but the O’Brian books, the Sharpe series, and the Flashman series all do the same thing. Flashman is almost a parody of the style.
Anyway, none of that actually matters. Carry on.
I would include Patrick O’Brien and make the genre a subset of Historical Fiction.
Flashman, the Cowardly, Dastardly Bastard as Protagonist, is surely a sub genre to his own.
Reread them of course. Now that we have the Internet, I can look up all those historical references and flesh out Flashy’s contribution to world peace in a whole new perspective.