Depends on what coin you are talking about. For most people Bitcoin is probably not going to be worth your time unless you are willing to invest for specialized computer hardware that is only useful for mining bitcoin. Which is essentially to say that you put yourself in a risky position where you are going into debt to get the hardware you need to make mining BTC and most other major Altcoins economically profitable.
However with that being said, if you can find a new altcoin that has good potential in terms of branding and technological improvements over what exists; then mining is not only reasonable but highly advisable. For example, Ravencoin is the current trending coin because it adds a new algorithm called X16 that makes it difficult for established miners with huge computational resources backing them up from being able to waltz in and just dominate over everybody else.
That is to say, Ravencoin has found a nifty way to address the “grandfather effect” where everybody who were early adopters of bitcoin (and thus became rich enough to build themselves essentially a supercomputer) ends up with an unfair competitive advantage on every other coin which uses a mining technique that is too similar to how bitcoin is mined.