I also like the spelling [name]Riley[/name], but I know I’d get a lot of people telling me it’s a girls’ name spelt that way, so what do you think of [name]Reilly[/name]? It’s also the original spelling of the name. 
I think [name]Riley[/name] is perfectly masculine, but it is a very common spelling. I think [name]Reilly[/name] is a nice way of adding originality to it without being tacky (think: [name]Rylee[/name], ugh!) and without having any pronunciation issues.
I like [name]Reilly[/name] a great deal. No one will have difficulty pronouncing it, but it looks much more serious and established than [name]Riley[/name], and more masculine as well.
I prefer the spelling [name]Riley[/name]! I do love it on a boy though.