I still like Chikorita because you can actually have an element of surprise in your strategy. with Meganium, there're tons of good options for movesets, but as much as i love the other two, you always know what's coming. Typhlosion almost always has Flamethrower, Thunderpunch, Earthquake, and one random filler move. and Feraligatr usually has four of the list of: Surf, Ice Beam, Earthquake, Crunch, and Ancientpower, sometimes with a filler move as well. the Meganium can come out with plenty of strategies. it can be a pseudo passer with Reflect, Light Screen, and Safeguard (though i don't like that one), it can come out with Ancientpower covering its offensive weaknesses, it can learn Swords Dance to power up, it can heal with Synthesis, it can use Counter against fliers and bugs, the list goes on.
...sorry. i went on for a while. but nobody gives Chikorita enough credit.