Sunday becomes a special day if you make it as such. For instance, if you set it aside for all the fun, fulfilling and relaxing moments with yourself or loved ones, it would definitely be a special day. On the other hand, if you do those things on other days, Sunday becomes Just another regular day.
I don't go for worship, have fun or do entertaining things on Sundays. So Sunday is just another regular day and I take it as it comes. I have friends that wear their best clothes and cook their favorite meals on Sundays.They go out and have fun too. So for them, Sunday is probably the best day of the week since they do regular things every other day of the week.