I find songs a bit boring without a solo break. Doesn't have to be guitar, and yes, best if it fits the song of course! I listened to a fair degree of 80s 90s metal back in the day, and quite often the solo was a bit rubbish. You need a decent solo that adds to the song - for example, Brian May's playing on These are the days of our lives - short and sweet but so compliments the whole song.
I'm not into loads of singing over everything, for me the best songs have plenty of 'musical' space. Yeah, I'm a prog fan!