I see investment as a stable low risk term. I love block chain technology and think that if implimented properly could produce a great efficiency gains and cost reduction. Even with my bias to the technology and my liking of private transactions, all altcoins are illiquid and unstable. They would be better speculation tools, but their lack of liquidity means that when the bubble bursts you could be very rich or very poor.
I like to think that investment as separate from speculation so no I don't currently see any altcoin as an investment opportunity.
So all these years, you only invested in Bitcoin? I cannot blame you if that's what you think since a lot of these altcoins are really unstable in terms of price and majority fluctuates base on bitcoin's price. There are still established altcoins out there that is worth investing though .