Professionals making games with relatively deep pockets have said things like this,
3:55 into this talk Luke Muscat says he took his inspiriation for Jetpack Joyride from that helicopter game everybody's seen.
Obviously JJ is way beyond that helicopter game in terms of execution, delivery and the things they built around it (just listen to the part near the end where he talks about how they developed the goals system). I can't see helicopter guy suing Halfbrick for what he's done, even though he openly admitted the basic mechanic of his game is based on it.
Was this a mistake by Muscat? I'd like to hear someone say otherwise.
I also heard various other programmers (such as John Carmack) say things like Commander Keen was all about bringing side scrollers such as Super Mario Bros to the PC (he specifically says "we had a nintendo there, we were playing Super Mario 3, that is what we set out to do as we were making those games on there, we wanted to bring the console experience to the PC")
So anyway, keep in mind the game makers that end up citing other games, when you look at the "derived" game or the game it cites as an inspiration, there's no way you could say the "derived" game "ripped off" the other. The game they made and the game cited as inspiration (more so for the Commander Keen/Mario comparison than for Jetpack Joyride) are totally different. I mean these developers are smart, they developed something cool and unique, and they didn't do some blatant plagiarism such as rip art or sprites from other games.
Anyway the gaming community is pretty critical and will probably accuse you of ripping off 10 other games you've never played before than the inspiration you cite.
So in short, no don't worry about citing your inspiration at a high level. There are 10k side scrollers, and 40k fps, and 90k RTS's. If people sued each other for minor similarity in play, there would be but 3 games for us to play.
But yes, don't blatantly rip off artwork or copy-protected stuff that anyone in their right mind would go after you for. Don't make a clone of a game and try to pass it off as your own idea.