I don't think investing in Litecoin is a bad idea, maybe LTC is not comparable to BTC but it also has its own strengths.
Not sure about you, but I'd rather invest everything in the solid final product than the experimental lab rat where a lot more things can fail.
LTC has more numbers than BTC
Doesn't matter. XRP has a total supply of 44 billion vs LTC's 64 million. Definitely doesn't make XRP a better investment.
LTC has a higher transaction speed than BTC
Doesn't matter. Higher transaction speed in sacrifice of security and decentralization. If transaction speed was the reason why I'd invest in a cryptocurrency, I'd be using and investing in PayPal instead.
Currently LTC is still in the top 10 largest currencies in the market, so LTC is still a worthwhile investment.
So is XRP, so is BCH, so is BSV, so is EOS. Market cap ranking doesn't matter that much as it's mostly an inaccurate statistic in the first place.