My objective answer is to organise it in whatever way you find most intuitive to keep track of your own collection. There isn't a right or wrong answer, so organise them however makes the most sense to you.
My less objective response...MLPMerch is not a G1 site; its organisation is horrible. It is the best site hands down for anything G4, as the owners are G4 experts - but sites that specialise in one generation don't necessarily provide good information for others. Wiki's timeline is messy in places but is probably better for G1 than other gens. Strawberry Reef remains good for G3 but not any other generation. I don't know if you collect G2, but Lavender Lagoon remains the best site in my opinion for that.
If you want an accurate list, it's never a good idea to use one site for all generations. It's better to use each site for the generation they specialise in.
There is no accurate book for G1 pony releases outside the US. I know someone in Europe is working on one but it is not yet at a point of print.