My favourite starter from HG/SS was Cyndaquil, at least it was my most used starter every time I played it. Chikorita had problems early on and Meganium was never particularly inspiring as a starter, and why would I use Feraligatr when I have a plethora of new Water types to use? Typhlosion was one of a few decent Fire types (outside of Magmar, Arcanine/Ninetales and possibly Flareon) and had a solid movepool, capable of learning Focus Blast and Earthquake through TM and knowing Lava Plume and Flamethrower early-ish on as well. Swift wasn't terrible and Quick Attack had it's uses through level-up and Fire was a great typing against Bugsy (a constant nightmare), Jasmine, Pryce (sort of) and helped a lot against Koga and Karen during the E4.
Feraligatr was probably my second favourite, it had better level-up moves with Bite, Ice Fang and later getting Surf and Crunch which was cool. I personally prefer Croconaw for some reason, but Feraligatr was solid. I just found myself wanting to use Pokemon like Quagsire, Politoed, Lanturn, Gyarados and Lapras instead. Meganium was decent, but didn't feel decent enough when you had it. I might have to play through the games with it again though before I confirm that decision. It's alright though, none of the Johto starters are bad.