1) It gives me a great pleasure to be here with you today. This sentence is NOT perfect. The minimum change you MUST make is to remove "a", so it reads, "It gives me great pleasure to be here with you today." But that sounds too wordy for my ear. Don't tell us about the giving, and you don't need to tell us where we are (we all know we are "here") just say: "It's a great pleasure to be with you today." 2) I'd like to express that I'm happy to be here with you today. This sentence, although correct, feels like the point you want to make is that you want to express something. Why are you telling us that you want to express something? Just express it: "I am happy to be here today" OR "I am happy to be with you today." 3) I'd like to express how I'm delighted to be here with you today. In addition to the issues mentioned above, the only important change I would make is to move "I'm" to the position just after "delighted", so that it reads: "I'd like to express how delighted I am to be here today" OR BETTER, "I'm delighted to be here today" OR "I'm delighted to be with you today". With the exception of the removal of "a" in the first sentence (which is a must), these suggestions are to make your language more efficient. But, of course, if you like your language a little stuffy and flowery, use it.