Litecoin is different from Bitcoin in the following ways, however none of them are particularly useful and on the contrary are only less worthy.
84 million vs 21 millions: since Bitcoin is divisible upto atleast nine decimals and also micro BTC can be used for dealing with low amounts
Faster blocks, 2.5 minutes vs 10 minutes average: six confirmations of Bitcoin are not equivalent of six confirmations of Litecoin, so Litecoin payments are usually confirmed after many more confirmations. It also wastes mining power because in Litecoin, most of the time miners may start work with non-best blocks.
scrypt vs SHA-256: since scrypt can be relatively efficiently run on CPU/GPU, it means botnets can easily control a lot of hashing power. Also, scrypt is relatively less analyzed and used than SHA-256, so it may not be more secure than SHA-256.
Technically, Bitcoin does what Litecoin does in an equal or better way. Also, Bitcoin testnet can be used to experiment with new features.
Why do we need Litecoin that actually has monetary value (around USD2.7 per LTC now)? Is it just promoted by a group of people who missed the Bitcoin get-rich boat?
Bitcoin is a novel concept and early adopters rightly earn their rewards for the risk they have taken.