Won't use the 'R' word. But all joking aside Terry has a fair bit in common with Tolkien as a writer, even in terms of output (will come back to that one), but they are both products of their 'age'. They both effectively 'made it all up', heavily influenced by other sources - Tolkien with existing myth (not all of it Nordic) and Terry with other types of fantasy since the genre was more widespread by the time he came to it (remember he was born in 1948 over 10 years after the Hobbit published).
Their stylistic differences are self-evident, but they both use humour suited to their respective era and their writings all contain deeper motifs of a philosophic nature which are essentially humanist, although Tolkien follows more religious-based themes, sometimes in a very modern manner (those elves again - although highly monogamous, had no central concept of socially recognised marriage, just the physical consummation and exchanged vows of fidelity between the 2 principals were all that was required and could be easily, albeit rarely, dissolved ).
So The Hobbit and CoM/LF have quite a bit in common, in that they are less than satisfactory for most fans, compared to later works, but were commercially successful in their own right. They're not too different in 'conceptual' terms also. Neither of them come up to the mark in terms of the functionality of the worlds they're introducing, but both describe it well enough to draw the readers into it and it has enough charm to enchant them into staying with it and to read the following book(s). The real differences as authors, is not in output, but approach. Tolkien wrote as least as much as Terry has, but most of it is only of academic interest and a lot of that is language-based. Arda was Tolkien's passion - an intellectual 'hobby' project he lived and breathed. Terry's approach is also scholarly, but more science than art in some respects and although it's probably his passion as well, it's also his living.
So finally affection... I read the LotR before I read The Hobbit about 18 months later when I was already obessed with Middle Earth. I read Discworld from book 1 and was hooked almost from p.1. Maybe it's that simple - you pick up your first book, 'click' with it and read the rest, so reading order is
important in some respects. If Jeff and Sharlene had picked up CoM back in 1983, when there were
no other better crafted Discworld books in existence, then they possibly wouldn't have bothered to pick up any more of them as they appeared, because they would still have thought CoM was badly written rubbish with a horrible cover (in Sharlene's case
I don't hate or even mildly dislike the Hobbit - it's a wonderful kid's book, fun, pacey and not too 'easy' or wrapped in cotton wool and like the Potter books (sort of...
) appeals to adults too - if I'd had kids I would definitely have read it to them. I don't compare The Hobbit to the LotR and certainly not the Silmarillion (which I have no affection for whatsoever, but value very highly as a reference book) and definitely not to the Children of Hurin story (it was merely boring in the Sil and not even the incest plot shocker of brother unwittingly marrying his unknown younger sister could make this cobbled together, mix and match book anything more than completely pointless - it has great illustrations though
). I just enjoy the 'proper' books for what they are and use the rest to 'play' with and make good RP characters.