Two broader thoughts that have come up in discussions elsewhere.
1.) Luke-Jr stated the other day that he foresees ring signature functionality being implemented into Bitcoin in 2-3 years. My response was that even if that actually happens, it wouldn't have a mandatory mix-in level, limiting the anonymity capabilities that Bitcoin could offer with it. However, I've heard others state that you actually wouldn't need a mandatory mix-in level for it to impart "good enough" anonymity for it to kill interest in anything else. Regardless of whether this is true or not, it does sound like something that could steal some remaining thunder from the anonymity-niche coins, given that Bitcoin already has a huge market share.
2-3 years is optimistic for a blockchain that's been bickering over the size of blocks for years now. And yes, you do need minimum mixin levels to make the system secure, although there are ways of doing that within a Bitcoin softfork. However, this presents the problem of money going from non-anonymous addresses to anonymous addresses, which makes blacklisting/censorship really easy (CoinBase can see your output entered into a ring signature output and ban you). Blacklisting in Monero will be impossible.
This is exactly why gmaxwell and andytoshi proposed their Bitcoin sidechain, which uses BRS (Bytecoin Ring Signatures), much like Monero, but using Bitcoin. However, it's likely that the majority of Monero will already be distributed by the time this is released (if ever), and at that point channels to and from Bitcoin, along with much better liquidity, should already exist.
2.) I've had discussions recently with Bitcoin maximalists who claim that anything built on an altchain cannot succeed, because Bitcoin's blockchain will remain by far the longest chain, and any other altcoin based on a PoW altchain that *ever* begins to compete with Bitcoin for market share will cause interested parties to attack it with the magnitudes of greater resources that are behind the Bitcoin network. My thought on this was that given that Monero uses a different hashing algorithm than Bitcoin, the resources behind Bitcoin couldn't be redirected at Monero in any direct sense (especially if the predominant resources behind Bitcoin are ASICs). Now, that isn't to say that there couldn't *still* be enough incentive involved, if Monero ever became more popular, for Bitcoin supporters to attack Monero by devoting fresh resources/energy to attack it. Thoughts?
The Bitcoin shills are always going to say that nothing will be better than Bitcoin, because all their money is in Bitcoin.
Monero is different. Monero is digital cash, whereas Bitcoin is a hybrid equity-wiring service. Bitcoin has a fixed distribution amount and transparency amongst investors. Conversely, Monero inflationary, like real cash, with a small distribution period of approximately five years as basically an "ICO". It can be spent with privacy, like real cash. They're different entities, with a different promise.