I am so fried that I don't think I can come up with ten books in one particular category so X will be a random variable as well.
Another way of getting into Discworld is to skip a few books (I know, I know - I am one of those obsessives who wants to start with the first book too) and start with a slightly later book. Pratchett's writing style evolves significantly from say the first five published books and the later ones. As one of the best starting points to one of the most popular story arcs I would suggest Guards! Guards! which is the first novel about the Ankh-Morpork City Watch. The writing is on even footing and you get introduced to several important characters in the Discworld universe.
A second approach is to read Wyrd Sisters the second book in the Witches story arc. Skipping Equal Rites won't be a problem, it is really different from the remaining witches books and since it was the third Discworld book Pratchett wrote it is still very similar to The Color of Magic and The Light Fantastic. Ideally you would read the books in publication order and see how he evolved as an author, but if the first book is giving you trouble any of these suggestions should work to give you a better entry into Discworld.
2) Dorthy L Sayers' Lord Peter Mysteries - this is another author whose first book in a series is quite different in style and tone than their later books. Whose Body? can be a rough introduction and turn a person off to the rest of the books, which is shame. The characters are not fully formed yet, coming off more as caricatures than people and the tone is a bit confused. Rather than starting with the first published book, I find that it can be easier and more fun to start with Murder Must Advertise. While technically the tenth book, the story is extremely self-contained so that you get to know the major characters (excluding Harriet) without being overwhelmed by details. Another way in is to start with the first Harriet Vane book - Strong Poison, but Peter comes off as a little weird in that one - it might be better to get to know him first.
4) If you are interested in Sherlock Holmes, I would suggest starting with The Adventures of Sherlock Holmes and not A Study in Scarlet, which is a much rougher book in style.
Sigh, I have run out of time and brain cells so I will stop here.